
==== Front
Hum Vaccin Immunother
Hum Vaccin Immunother
Human Vaccines & Immunotherapeutics
2164-5515
2164-554X
Taylor & Francis

39233398
10.1080/21645515.2024.2395685
2395685
Version of Record
Brief Report
Public Health & Policy
Timeliness for vaccination according to the expanded immunization program in children under 6 years of age in Colombia between 2014 and 2019
J. E. MACHADO-ALBA ET AL.
HUMAN VACCINES & IMMUNOTHERAPEUTICS
https://orcid.org/0000-0002-8455-0936
Machado-Alba Jorge Enrique a
https://orcid.org/0000-0001-8458-0986
Machado-Duque Manuel Enrique a b
Gaviria-Mendoza Andrés a b
Vargas-Zambrano Juan C. c
a Grupo de Investigación en Farmacoepidemiología y Farmacovigilancia, Universidad Tecnológica de Pereira-Audifarma SA , Pereira, Colombia
b Grupo de Investigación Biomedicina, Facultad de Medicina, Fundación Universitaria Autónoma de las Américas , Pereira, Colombia
c Global Medical Vaccines, Sanofi , Lyon, France
CONTACT Jorge Enrique Machado-Alba machado@utp.edu.co Grupo de Investigación En farmcoepidemiología Y Farmacovigilancia, Universidad Tecnologica de Pereira-Audifarma SA, Calle 105 No. 14-140, Pereira, Risaralda 660003, Colombia.
4 9 2024
2024
4 9 2024
20 1 2395685Integra02 9 2024
Integra02 9 2024
04 6 2024
05 8 2024
19 8 2024
© 2024 The Author(s). Published with license by Taylor & Francis Group, LLC.
2024
The Author(s)
https://creativecommons.org/licenses/by-nc/4.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent.

ABSTRACT

The aim was to estimate the vaccination timeliness defined as the proportion of children under 6 years of age who received their immunization in the time range established by the Colombian Expanded Immunization Program (EIP). A retrospective cohort study that collected reports of vaccination opportunities between 2014 and 2019 provided by the Ministry of Health. Age, sex, city, ethnicity, health system affiliation regimen, vaccine applied, and timing of vaccination were considered for the time range under study. A total of 3,370,853 immunized children were included from all regions of the country. More than 80% of children had a timeliness to get most vaccines. The exceptions were yellow fever (17%) and seasonal influenza (42%). No differences in timeliness were found according to geographic region or by health system affiliation regime, but the average timeliness for all vaccines of children of the indigenous population (65.8% ±18.4%) was lower than that of the rest of the population (78·6% ± 19·3%) (p = 0·021). The timeliness for vaccination under the EIP of Colombia is high, with proportions of 72–96%, but intergroup differences were identified, mainly lower timeliness among indigenous people. These findings warrant improvement strategies that would guarantee the immunization of the entire child population.

KEYWORDS

Colombia
immunization
immunization program
vaccine-preventable diseases
Universidad Tecnológica de Pereira Sanofi 10.13039/100004339 ID PER00095 Sanofi 10.13039/100004339 This collaborative work with Universidad Tecnológica de Pereira was funded by Sanofi [under Grant: ID PER00095]. Sanofi did not participate in the management or data analysis of the study data.
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pmcIntroduction

Child vaccination is one of the most cost-effective processes and interventions in public health, so its correct implementation and access among the entire population of a country should be a priority. Childhood vaccination can reduce by more than 90% or even 100% most preventable infectious diseases,1 as evidenced by the eradication of smallpox,2 the targeted eradication of oral polio by 2026, and the dramatic decrease in cases of infectious disease caused by Haemophilus influenzae type B (HiB).3–6

Vaccination programs offer a benefit not only for the immunized child but also indirectly for the entire community by adding to the effect of herd immunity,7 protecting those people who are not vaccinated or in whom immunity has decreased. This herd effect appears when many people in a population are immunized, reducing the probability of transmission within it.8 For this reason, the widespread application of vaccination programs is of utmost importance. To optimize vaccine implementation, we must know the indicators of coverage and timeliness in the application that will allow us to assess the capacity of the programs and identify possible opportunities for improvement.

In Colombia, reports on the Expanded Immunization Program (EIP) show quite high coverage, such as > 90% for traditional vaccines such as BCG, pentavalent against diphtheria, pertussis, tetanus, HiB and hepatitis B (DPT-HiB-HBV), oral polio, and triple vaccine against measles, mumps, and rubella (MMR), but slightly lower (~80%) for recently introduced vaccines such as rotavirus and only 48·4% for influenza.9 In addition, there are still problems with the timing of administration of vaccines (delays in vaccination), which is a potential problem for the success of the program.10–12

Colombia’s EIP includes the use of mono- and polyvalent vaccines for at least 17 preventable infectious diseases that are offered to all children from 0 to 5 years of age at no added cost to the family. National data show that vaccination coverage is good for most vaccines, but details are scarce on the gaps between when the vaccines should be given and when a child is actually immunized, which determines the timeliness with which said vaccine is applied (see Supplementary Table 1). It should be taken into account that vaccination times are also important for the adequate prevention of diseases that can be avoided by vaccination, reducing the cases and associated costs, especially for the first doses such as HBV. In the latter case, several studies have shown the importance of receiving it in the first 24 hours of life to reduce the vertical transmission of the virus, which is its main form of infection. For this, the World Health Organization has set the goal that by 2030, 90% of newborns will receive their first dose of HBV vaccine in the first 24 hours of life.13,14 It is estimated that if this were achieved, 710,000 deaths could be prevented among those born between 2020 and 2030, and elimination in the Americas could be achieved by 2030.15 The time of application of each vaccine is designed and recommended to achieve age-specific immunity, seeking that the child achieves immunity at the right time and as early as possible, with little space for applications prior to or after what is recommended, and although there are some recommendations from the WHO, it is provided that each country designs the vaccination windows according to local epidemiology, availability of resources and public policies, which is why not only the application of the biological product is important to achieve adequate immunity but also the time of its application.16,17Table 1. Indicators to measure timeliness of immunization according to the Colombia expanded immunization program in children under 6 years of age.

Vaccination Opportunity (Timely application) Indicator	Timely application description	
Opportunity in BCG vaccination in the newborn	Number of children between 1 to 11 months vaccinated in the first 29 days with BCG/Total children 1 to 11 months surveyed x 100	
Opportunity for vaccination with Hepatitis B in the newborn	Number of children between 1 to 11 months vaccinated in the first 29 days with hepatitis B/Total children 1 to 11 months surveyed x 100	
Opportunity in vaccination with the first oral polio dose	Number of children from 3 to 11 months vaccinated with the first dose of oral polio between 2 months and 2 months 29 days/Total of children from 3 to 11 months surveyed x 100	
Opportunity in vaccination with the second oral polio dose	Number of children aged 5 to 11 months vaccinated with second dose of oral polio between 4 months and 4 months 29 days of age/Total of children aged 5 to 11 months surveyed x 100	
Opportunity in vaccination with the third oral polio dose	Number of children from 7 to 11 months vaccinated with third dose of oral polio between 6 months and 6 months 29 days of age/Total of children from 7 to 11 months surveyed x 100	
Opportunity in vaccination with the first pentavalent dose	Number of children 3 to 11 months vaccinated with the first dose of pentavalent between 2 months and 2 months 29 days months of age/Total children 3 to 11 months surveyed x 100	
Opportunity in vaccination with second dose of pentavalent	Number of children 5 to 11 months vaccinated with second dose of pentavalent between 4 months and 4 months 29 days of age/Total children 5 to 11 months surveyed x 100	
Opportunity in vaccination with third dose of pentavalent	Number of children 7 to 11 months vaccinated with third dose of pentavalent between 6 months and 6 months 29 days of age/Total children 7 to 11 months surveyed x 100	
Opportunity in vaccination with first dose of rotavirus	Number of children vaccinated with the first dose of rotavirus between 2 months and 2 months 29 days of age/Total children between 3 and 11 months surveyed x 100	
Opportunity in vaccination with second dose of rotavirus	Number of children 5 to 11 months vaccinated with second dose of rotavirus between 4 months and 4 months 29 days of age/Total children between 5 and 11 months surveyed x 100	
Opportunity for vaccination with first dose of Pneumococcal vaccine	Number of children vaccinated with the first dose of Pneumococcal vaccine between 2 and 2.29 days of age/Total children between 3 and 11 months surveyed x 100	
Opportunity for vaccination with second dose of Pneumococcal vaccine	Number of children 5 to 11 months vaccinated with second dose of Pneumococcal vaccine between 4 months and 4 months 29 days of age/Total children between 5 and 11 months surveyed x 100	
Opportunity for vaccination with seasonal influenza	Number of children 6 months vaccinated with dose of seasonal influenza vaccine between 6 months and 29 days of age/Total children between 6 months and 29 days surveyed x 100	
Opportunity for vaccination with second dose of seasonal influenza	Number of children 12 to 23 months and 29 days vaccinated with dose of seasonal influenza vaccine between 12 months and 23 months 29 days of age/Total children between 12 and 23 months 29 days surveyed x 100	
Opportunity in vaccination with Measles – Mumps – Rubella (MMR) vaccine	Number of children aged 16-23 months vaccinated with Measles – Mumps – Rubella (MMR) vaccine doses between 12 months and 15 months 29 days of age/Total children between 16 and 23 months surveyed x 100	
Opportunity in vaccination with yellow fever	Number of children aged 16-23 months vaccinated with yellow fever between 12 and 15 months and 29 days of age/Total children between 16-23 months surveyed x 100	
Pneumococcal booster vaccination opportunity	Number of children aged 16-23 months vaccinated with pneumococcal booster between 12 months and 15 months 29 days of age/Total children aged 16-23 months surveyed x 100	
Opportunity for vaccination with DPT first booster	Number of children aged 22 to 35 months vaccinated with first DPT booster between 18 and 21 months of age/Total children aged 22 to 35 months surveyed x 100	
Opportunity for vaccination with oral polio first booster	Number of children aged 22 to 35 months vaccinated with first oral polio booster between 18 and 21 months of age/Total children between 22 to 35 months surveyed x 100	
Second booster DPT vaccination opportunity	Number of children from 64 to 71 months vaccinated with second DPT booster between 60 months and 63 months 29 days of age/Total children between 64 to 71 months surveyed x 100	
Opportunity for vaccination with second oral polio booster	Number of children from 64 to 71 months vaccinated with a second oral polio booster between 60 months and 63 months 29 days of age/Total of children between 64 to 71 months surveyed x 100	
Opportunity for vaccination with triple viral booster	Number of children from 64 to 71 months vaccinated with Measles – Mumps – Rubella (MMR) vaccine booster between 60 months and 63 months 29 days of age/Total of children between 64 to 71 months surveyed x 100	
Adapted from guidelines for evaluation of coverage, timeliness and completeness of vaccination scheme, Expanded Immunization Program, Colombia.

The Colombian health system offers universal coverage to the entire population through two membership regimes, one contributory, or paid by the employer and worker, and the other subsidized by the state. They both cover all vaccines in the expanded immunization program. The Ministry of Health sends vaccines to all regions to be administered without any cost in hospitals, health centers, vaccination posts, and vaccination campaigns in remote areas to ensure that they are administered to all children. Considering the above and the lack of information on the opportunity for vaccination in the country, this study estimated the timeliness for vaccination in Colombian children under 6 years of age for all vaccines that are included in the EIP.

Materials and methods

A retrospective cohort study was conducted. Which included the data from the reports made on the vaccination opportunity carried out by the departmental, district, and municipal health secretariats in Colombia. These reports were in children born between the years 2014 and 2019 and that were provided by the Ministry of Health of the country in individual files for each year of follow-up in electronic spreadsheets, based on the information from the vaccination report of each child who goes to be vaccinated at an authorized health organization. Always protecting the anonymity of the children, the data were delivered and managed by age group, biological variables, affiliation regime, and geographic region.

The data of all children under 6 years of age of either sex with vaccination cards reported to the Ministry of Health were included. The data was provided by the Ministry of Health from the reports made of vaccination of each child carried out in health care organizations or in vaccination campaigns, and collected data from 100% of the children actually vaccinated. Those that were duplicated in the national databases were excluded (identified from the Unique Identification Number), but those that had a duplicate record led to the elimination of the other records and the one from the first time it was identified was retained. Records with inconsistent data such as vaccination dates before the date of birth and absence of a reported date of birth were excluded too. In addition, as a control filter, children who were missing from the BCG registry, to which submission is mandatory in the first 28 days of life, were excluded because this lack of registration indicated the data of such infants were not reliable.

The database was validated by the research team in search of inconsistent data. The following groups of variables were considered: Sociodemographic: age (in months), distribution according to age group (0 to 11 months; 12 to 23 months; 24 to 35 months; 60 to 71 months), municipality and department of residence, ethnicity, affiliation regime to the health system (Contributory regime (which is paid by workers and their employers) and subsidized regime (paid by the state to cover people without employment or without the ability to pay)).

Vaccination: Each vaccine included in the Colombian Expanded Immunization Program (EIP) that was registered in the vaccination card of each child was identified with the date of administration.

In Supplementary Table S1 are listed the vaccines that are included in the program by age group.18

(3) Vaccination timeliness: The administration of each vaccine was categorized as timely if it was in the age range allowed according to EIP (guideline for the evaluation of coverage, opportunity, and complete vaccination schedule) up to 29 days from the recommended age (See Table 1, Definitions of timely application for Colombia). The timeliness for each vaccine was finally obtained as the proportion of children with timely application in relation to the total number of children in that age group, which was adjusted for each year. The denominator for calculation is all vaccinated children (timely + late).

From these data, a dataset was built that was analyzed in Python 319 using the libraries Pandas 1.4.120 and Numpy 1.24.3.21 A first exclusion process was carried out according to the criteria above, followed by the validation of the outlier data, and the remaining data were unified in terms of year, geographical region, and application registration date format.

Statistical analysis

For statistical analyses, the statistical package SPSS version 26 for Windows (IBM, USA) was used. Univariate analyses were performed considering that the immunization was timely according to the date of birth and the date of administration application of each vaccine during the time considered appropriate by EIP for each of the children who were finally included (see Table 1), frequencies and proportions were calculated. The vaccination timeliness was calculated by region, type of insurance, and ethnicity. Differences in timeliness between groups of vaccinated children (ethnicity and affiliation regime) were tested using the Mann – Whitney U test (normality was assessed using the Shapiro – Wilk test). Values of p < .05 were considered significant.

Bioethical considerations

The protocol was approved by the Bioethics Committee of the Technological University of Pereira in the category of research without risk, as established by Resolution 8430 of 1993 of the Ministry of Health (Approval code: 01-14-12-20). The ethical and confidentiality principles of the information established by the Declaration of Helsinki were respected.

Results

Between 2014 and 2019, 5,268,582 children were identified who were immunized in the country, of whom 1,897,729 were excluded because they had no report of the BCG vaccine. The final analysis was made with 3,370,853 children under 72 months of age which corresponds to 74·2% of the children vaccinated in that period in Colombia. Figure 1 shows a flow chart with the causes of exclusion of infants. The geographical area that contributed the highest number of vaccinated children was the Caribbean region, followed by the Central and Eastern regions, while 7·3% had no record of residence. Table 2 shows the number of children who were included in the analysis for each year evaluated and the status of affiliation to the health system, which showed a large majority of children affiliated with the subsidized regime. Figure 1. Flow chart with the causes of exclusion of infants.

Table 2. Distribution by year, geographic regions, affiliation regime of 3,370,853 children vaccinated with the Colombia expanded immunization program scheme between 2014 and 2019.

 	Number of children	Percentage	Number of excluded children	Percentage within excluded	
 	n = 3,370,853	 	n = 1,897,729	 	
Year	 	 	 	 	
2014	606,352	18·0	534,759	28·2	
2015	567,099	16·8	485,146	25·6	
2016	553,370	16·4	459,777	24·2	
2017	558,476	16·6	415,458	21·9	
2018	558,868	16·6	1420	0·1	
2019	526,688	15·6	1162	0·1	
No data	0	0·0	7	0·0	
Geographic regions	 	 	 	 	
Caribbean	904,098	26·8	443,783	23·4	
Central	715,802	21·2	354,712	18·7	
Oriental	510,719	15·1	245,745	12·9	
Pacific	469,581	13·9	237,672	12·5	
Bogotá-Cundinamarca	467,543	13·8	238,581	12·6	
Amazonia	53,691	1·5	25,898	1·4	
Without record	249,419	7·3	351,338	18·5	
Affiliation regime to Health System	 	 	 	 	
Subsidized	1,938,286	57·5	680,018	35·8	
Contributory	1,159,439	34·4	669,588	35·3	
Other/Without record	273,128	8·1	548,123	28·9	

For the majority of vaccines included in the EIP, a timeliness with proportions greater than 80% could be identified, with the exception of yellow fever and seasonal influenza, which were between 17.1% and 41.8% (Table 3). The timeliness was lower in vaccines that were administered after 6 months of age, particularly the third doses of pentavalent and oral polio. Regardless of vaccine in the six months after birth, there was a decrease between the first doses and the boosters, being higher for the first dose usually given at 2 months than for the third dose at 6 months.Table 3. Percentages of timeliness according to vaccine and age of 3,370,853 children vaccinated with the Colombia expanded immunization program scheme between 2014 and 2019.

Age group	Age	Vaccine	Dose	Timely application	N Group*	%	
0 – 11 Months	At birth (0 to 28 days)	BCG	Single	3,242,872	3,370,853	96.2	
Hepatitis B	At birth	2,394,732	3,283,005	72.9	
2 Months	Pentavalent	Diphtheria – Pertussis – Tetanus (DPT)	Initial dose	2,404,325	2,639,922	91.1	
Haemophilus influenzae type b (Hib)	
Hepatitis B	
Oral Polio	Initial dose	2,396,828	2,738,263	87.5	
Rotavirus	Initial dose	2,379,964	2,633,008	90.4	
Pneumococcal	Initial dose	2,334,941	2,738,719	85.3	
4 Months	Pentavalent	Diphtheria – Pertussis – Tetanus (DPT)	Second dose	2,203,793	2,689,558	81.9	
Haemophilus influenzae type b (Hib)	
Hepatitis B	
Oral Polio	Second dose	2,192,831	2,678,669	81.9	
Rotavirus	Second dose	2,166,563	2,560,537	84.6	
Pneumococcal	Second dose	2,111,581	2,642,569	79.9	
6 Months	Pentavalent	Diphtheria – Pertussis – Tetanus (DPT)	Third dose	1,953,266	2,648,696	73.7	
Haemophilus influenzae type b (Hib)	
Hepatitis B	
Oral Polio	Third dose	1,942,967	2,639,922	73.6	
Seasonal Influenza	Initial dose	921,557	2,204,241	41.8	
12 – 23 Months	12 to 23 Months	Seasonal Influenza (booster)	Second dose	1,171,162	1,538,126	76.1	
12 Months	Measles – Mumps – Rubella (MMR)	Initial dose	2,420,185	2,618,647	92.4	
Varicella	Initial dose	2,202,435	2,407,671	91.5	
Pneumococcal	Booster	2,345,935	2,531,981	92.7	
Hepatitis A	Single	2,397,767	2,611,492	91.8	
18 Months	Diphtheria – Pertussis – Tetanus (DPT)	First booster dose	1,949,349	2,467,255	79.0	
Oral Polio	First booster dose	1,946,823	2,470,049	78.8	
Yellow fever (YF)	Single	426,069	2,491,307	17.1	
>24 Months	5 Years	Diphtheria – Pertussis – Tetanus (DPT)	Second booster	972,647	1,111,710	87.5	
Oral Polio	Second booster	963,692	1,102,903	87.4	
Measles – Mumps – Rubella (MMR)	First booster dose	966,376	1,121,630	86.2	
Varicella	First booster dose	ND	 	ND	
*N Group: corresponds to the total denominator of children with a vaccination record for their age. ND: No Data Reported.

The timely administration has proportions higher than 86% for the 12-month vaccines and the boosters at 5 years of age, being higher than the doses applied as a booster at 18 months where the timeliness was 79·9%. (see Table 3).

Although the vaccination opportunities were similar, they were not always the same for all vaccines administered at the same age, and a greater difference was noted between the first dose of the oral polio vaccine and DPT at 2 months of age (3·6%) and pneumococcus and DPT in the same group (5·8%).

The assessment of the timeliness by geographic region of the country did not yield great differences. However, in the comparison of affiliation regimes, there were lower proportions of timely application in children belonging to the subsidized group and those who did not have any type of insurance (see Table 4). However, these differences were not statistically significant in the timeliness between all vaccines of the contributory regime population (median: 86·3%, interquartile range[IQR]: 80·3% − 91·9%) compared to the subsidized regime (median: 82·8%, IQR: 76·1% − 88·7%) (p = 0·174).Table 4. Percentages of timeliness by geographic regions, affiliation regime and ethnic group of 3,370,853 children vaccinated with the Colombia expanded immunization program scheme between 2014 and 2019.

 	BCG	HB	1 dose oral polio	2 dose oral polio	3 dose oral polio	1 dose penta valent	2 dose penta
valent	3 dose penta valent	1 dose rotavirus	2 dose rotavirus	1 dose neumococcal	2 neumococcal	Booster neumococcal	1 dose MMR	1 dose yellow fever	1 dose Hepatitis A	1 dose varicella	1 dose influenza	2 dose influenza	Booster Influenza	1 booster oral polio	1 booster DPT	2 booster DPT	2 booster oral polio	1 booster MMR	
 	%	%	%	%	%	%	%	%	%	%	%	%	%	%	%	%	%	%	%	%	%	%	%	%	%	
Geographic Region	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	
 Caribe	96·2	72·3	87·5	81·9	73·6	87·5	82·0	73·7	90·4	84·7	85·2	80·0	92·7	92·4	17·7	91·8	91·3	41·7	34·4	76·0	78·8	79·0	87·5	87·4	86·1	
 Central	96·4	74·0	87·6	82·0	73·7	87·7	82·1	73·9	90·5	84·6	85·4	79·9	92·7	92·5	15·9	91·9	91·6	41·8	34·6	76·3	78·9	79·1	87·5	87·3	86·1	
 Oriental	96·1	72·1	87·4	81·7	73·4	87·4	81·8	73·6	90·2	84·5	85·1	79·7	92·5	92·3	17·7	91·7	91·2	41·6	34·2	75·9	78·7	78·9	87·6	87·5	86·3	
 Pacific	96·1	73·7	87·4	81·7	73·5	87·4	81·8	73·7	90·3	84·6	85·0	79·7	92·6	92·3	16·3	91·6	91·2	41·9	34·6	76·2	78·7	78·9	87·4	87·3	86·1	
 Bogotá-Cundinamarca	96·3	73·3	87·7	81·9	73·5	87·7	82·0	73·7	90·5	84·5	85·4	79·9	92·7	92·5	16·5	92·0	91·6	41·8	34·5	76·6	79·0	79·2	87·4	87·3	86·1	
 Without record	96·1	72·6	87·7	82·1	73·9	87·7	82·1	74·0	90·6	84·9	85·6	80·4	92·8	92·5	19·1	91·8	91·3	42·3	35·1	75·7	78·8	79·0	87·5	87·5	86·3	
 Amazonía-Orinoquía 	96·2	71·0	87·4	81·8	73·5	87·5	81·8	73·6	90·2	84·6	85·3	80·2	92·9	92·4	18·5	91·8	91·3	42·5	35·0	75·7	79·1	79·2	87·7	87·7	86·5	
Affiliation regime to Health System	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	
 Subsidized	96·0	72·8	86·2	79·8	71·6	86·2	79·8	71·7	89·5	82·8	84·4	77·8	92·8	92·4	18·5	92·1	91·8	40·6	33·1	76·1	78·3	78·5	88·7	88·5	87·8	
 Contributory	98·0	72·6	91·9	88·4	80·1	91·9	88·5	80·3	92·5	88·6	89·9	85·7	93·4	94·6	14·1	94·2	93·8	44·8	37·6	76·7	82·0	82·3	86·3	86·3	84·4	
 Uninsured poor population	84·9	75·9	67·6	50·1	38·5	67·1	49·7	38·3	81·2	65·1	56·1	49·8	77·7	70·0	24·3	61·9	61·3	26·1	20·9	69·8	45·1	45·1	73·6	73·4	70·7	
 Exception and special regimes and INPEC	98·2	71·7	92·5	89·0	81·0	92·5	89·2	81·2	93·1	89·5	90·9	86·7	94·9	95·1	19·0	95·2	94·0	45·4	37·9	74·4	84·1	84·3	87·9	87·7	86·8	
 Without record	97·8	93·8	71·2	55·9	46·5	70·9	56·4	46·7	82·6	67·0	66·3	55·8	78·6	73·5	28·3	67·1	64·6	24·9	23·5	71·4	61·2	60·9	88·2	87·8	86·0	
Ethnic group	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	
 No ethnic group (mestizo)	97·4	73·8	88·9	83·5	75·2	88·9	83·6	75·3	91·0	85·6	86·5	81·4	93·1	93·0	16·8	92·4	91·9	42·4	35·1	76·7	80·0	80·2	87·9	87·8	86·5	
 Black or Afro-Colombian	94·5	68·6	84·2	75·5	65·8	84·2	75·5	65·9	88·3	79·4	82·0	73·1	90·4	90·4	17·3	90·0	89·9	39·8	31·6	69·0	71·1	71·2	82·7	82·4	81·3	
 Indigenous	75·4	61·9	66·1	58·3	52·8	66·1	58·3	52·9	80·1	69·9	65·4	58·4	86·5	83·4	22·8	83·2	83·1	32·8	25·2	73·4	65·2	65·2	87·1	87·1	86·2	
 Raizal	93·1	55·3	84·3	75·3	64·6	84·2	75·1	64·7	87·9	78·8	82·8	74·0	88·4	87·8	15·3	87·5	86·9	38·0	29·7	71·3	69·9	69·9	83·1	82·7	80·9	
 Other	96·4	57·2	88·6	87·5	81·4	89·1	87·5	81·0	90·4	89·8	86·2	85·6	93·4	93·8	16·0	93·0	93·1	47·4	37·9	77·2	84·5	84·8	90·5	90·6	90·0	
 Palenquero	93·6	59·6	83·4	75·3	64·4	82·7	75·2	64·5	88·1	79·3	80·1	72·4	91·2	92·2	16·4	90·6	89·5	35·7	32·1	63·8	74·4	74·4	86·1	85·9	86·7	
 ROM (Gypsi)	95·2	71·6	82·7	74·3	67·4	83·9	73·9	67·2	87·1	76·4	82·0	72·1	90·0	91·2	16·2	90·6	88·6	40·2	28·0	73·0	71·5	71·5	78·8	78·1	80·0	
 Without record	94·8	52·5	85·7	75·7	66·6	84·9	77·1	67·6	87·1	85·6	72·4	76·2	84·9	81·8	31·7	70·3	66·0	30·2	27·6	66·8	68·9	68·5	88·9	88·8	87·9	
Year	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	
 2014	95.9	45.7	85.7	81.4	74.9	85.8	81.6	74.9	88.4	84.4	85.3	82.0	92.9	91.2	45.8	91.2	87.4	42.3	35.1	68.4	78.0	78.2	88.5	88.6	87.0	
 2015	95.7	45.0	86.6	82.5	74.6	86.7	82.5	74.9	89.7	85.8	86.4	83.3	91.3	91.9	5.7	91.8	91.5	38.6	31.5	68.3	78.0	78.1	82.9	82.6	81.9	
 2016	96.0	60.6	90.2	81.4	73.6	90.2	81.7	73.8	93.4	85.1	83.0	72.8	91.3	91.6	10.3	89.2	90.5	34.6	29.3	75.4	78.2	78.4	90.5	90.3	89.9	
 2017	96.1	97.1	87.2	81.9	73.9	86.9	81.8	73.9	89.5	83.2	83.0	78.2	93.9	93.6	11.8	92.9	92.8	46.7	38.2	83.8	80.7	80.8	98.9	98.9	96.2	
 2018	96.3	97.4	87.4	82.5	74.5	87.4	82.7	74.6	90.2	84.9	86.0	81.9	94.2	93.9	13.9	93.5	92.9	48.6	39.5	78.8	77.0	77.2	0.0	0.0	0.0	
 2019	97.3	97.6	88.1	81.4	70.1	88.1	81.4	70.3	91.1	84.3	87.7	81.1	92.1	92.1	15.8	92.0	91.3	39.2	32.6	79.2	81.1	81.6	0.0	0.0	0.0	
MMR: measles, mumps, and rubella. DPT: diphtheria, pertussis, tetanus. INPEC: national penitentiary institute.

The vast majority of parents or guardians categorized their children as mestizos or without any particular ethnic group, and this group had the highest level of timely vaccination, while the indigenous population presented low timeliness values, < 60% for several vaccines (Table 4). The timeliness of application of all the vaccines of indigenous children (median: 66·1%, IQR: 58·3% − 83·1%) was lower than that of the rest of the population (median: 85·2%, IQR: 76·3% − 88·6%) (p = 0·002).

Discussion

This national study with the vaccination databases of the Colombian EIP could determine at the population level the timeliness for the administration of the vaccines included in said plans and identified different variables related to the type of vaccine, as well as the differences by region, affiliation regime and ethnic group. Although it is a study with a population between 2014 and 2019, due to the number of children included in the analysis, the representativeness of the entire country, and the results found, this information is of utmost importance for the construction of new public policies and the generation of strategies that seek to improve timeliness and coverage, especially in regions and population groups with greater vulnerabilities.

The first thing to highlight is the identification of a vaccination timeliness for BCG close to 96·2%, but it was only 65% for HBV, which is quite striking given that both are applied around birth at a time of close infant follow-up.18 It can be explained by some degree of lack of registration, and by the migration of populations from other areas, especially from Venezuela to Colombia, during the observation period.22

In a study carried out in Colombia, with a sample of 2457 children, it was found that the timeliness remained above 90% for almost all vaccines, except for influenza and yellow fever, a situation that is similar to that identified in this national study, since the first dose of influenza had an timeliness close to 42%, while that of yellow fever did not reach 18%.23 In the case of yellow fever, it has been identified that there are administrative problems, in the printing of the individual card used for this vaccine and sometimes with the supply, which may help explain the low opportunity for vaccination.24 There is a need for studies that evaluate the reasons and explain why these two vaccines in particular have lower rates of timely application. The findings would allow the creation of strategies that improve said timeliness and thus also improve protection against these diseases.23 A similar situation has been reported by Werk et al. in the United States, who identified that only 46·8% of infants received influenza vaccination at the appropriate dose and time, which may hinder protection against this infection.25

There was also evidence of a decrease in the administration timeliness for DPT vaccines with subsequent doses (81·9% in the fourth and 73·7% in the sixth month. Other times that showed lower timeliness were 6 and 18 months of age, compared with the vaccines that are applied at other ages, which can compromise immunization against DPT, HiB, HBV and oral polio. This situation also generates the need to work on the creation of strategies aimed at compliance and adherence to the recommendations of vaccination programs18,26 such as the use of combined vaccines between oral polio and acellular hexavalent DPT.

The timing of vaccination can vary between countries since each one may have its own childhood immunization program. The countries of the Americas, including Colombia, follow some international guidelines directed by the Pan American Health Organization, such as tolerating delays of up to 1 month from the recommended date of administration.27,28 An analysis carried out in Kenya, a low-income country, by Chiabi et al. identified a timely immunization for BCG in 83·2% of cases, for the first dose of DPT in 93·9%, and for measles in 94·8% but used a period of 2 weeks as the maximum limit from the ideal date of application. They also reported that the oral polio vaccine had the greatest difficulty in achieving timely application and that the variables associated with timing difficulties were preterm delivery and changes in the vaccination center.27

Other analyses carried out in the Americas, such as the one carried out by D’Ardenne et al. in Guatemala and Peru, showed worrying results on timely applications for the third doses of pentavalent that only reached 54·3% in Guatemala and 66·8% in Peru. While MMR was administered on time in 58.2% and 44·3%, respectively, although these two countries reported vaccination coverage of more than 90% in the same period, there are still factors that limit the timeliness rate, such as the low educational level of the parents and the greater number of children.29 In Colombia, the coverage for the third dose of pentavalent was close to 93% and for MMR to 57%,9 which raises concerns about the scope that vaccination programs have in South America to achieve the goal of prevention of these diseases. In cases of lack of timely application, catch-up programs must be established to achieve the highest coverage and guarantee the protection provided by vaccines to children, which has become especially relevant after the COVID-19 epidemic.30

The lower compliance with timely vaccination found in indigenous groups, as well as Raizales of the Caribbean islands, compared to other ethnic groups such as whites, mestizos, and even Afro-Colombians, can be explained by lesser access to vaccination programs and distrust in front of a health system different from that of their ancestral communities. These difficulties generate the timeliness to create new educational and approach strategies that achieve the application with the best timeliness and coverage to close the gap in the health results between these populations. Similar situations have been described for ethnic minorities in the United States, such as American Indians and Alaskan Natives, who have presented significant delays in childhood immunization programs and have reported that three out of four children do not get timely doses of some of the vaccines. The timeliness of application of all the vaccines of the children of the indigenous population (median: 66·1%, IQR: 58·3 - 83·1%) was lower than that of the rest of the population (median: 85·2%, IQR: 76·3 - 88·6%) (p = 0·002).31 However, the Colombian Ministry of Health establishes intensification strategies to guarantee the vaccination of children who did not attend in a timely manner, or who live in remote areas, in indigenous reservations or who have other access difficulties.32

A report in Michigan, United States, by Wagner et al. showed in 2010 that the timely application of all doses at 24 months of age was 22%, with individual values according to the vaccine that could vary for HiB between 48% and 57%;33 however, in Colombia, it is included in a single vaccine product called “pentavalent” that covers not only HiB but also DPT and HBV, which constitutes a strategy to increase the timeliness for vaccination by guaranteeing the application of all of them at a single moment. A Belgian study by Lernout et al.34 identified an application with a delay of one to 2 months for MMR of 22% and more than 2 months in 5% of children. In the case of the third dose of DPT, they reported a delay of 19% between 1 and 2 months and 11% of more than 2 months.34 These results show that the problems of timely application of vaccines in the pediatric population are not exclusive to developing or poor countries, because there are different situations, such as the existence of large families, changes in vaccination center, collection of some vaccines or absence of others at the points or centers of administration, which have been described in different studies and which may be targeted by the public health programs of the different countries.34–37

The results of this analysis show the quality of the country’s vaccination program. Timely application in high proportions for the vast majority of vaccines is a guarantee that the full benefits generated by the vaccine will be achieved. Early vaccination can result in suboptimal immunity due to interference with maternal antibodies, and delayed vaccination prolongs the exposure of children while they are susceptible to vaccine-preventable diseases and can lead to the appearance of isolated cases or epidemics.16 It is expected that these positive results will be reflected in a really low incidence of preventable diseases in Colombia, with the exception of indigenous communities, where cases of some of these diseases may occur.

This study has a few limitations. It used official data with the reporting formats of the Colombian Ministry of Health through the annual and routine survey that is carried out by the health services of each region of the country, which does not allow evaluation of additional information or the asking of questions other than those included in it, which may obscure the reality of vaccination and underestimate the timeliness rates in some particular regions, as well as not knowing the reasons for non-vaccination or lack of timely vaccination. It was also not assessed whether the lack of timely application was due to application before (early vaccination) the date or late (delayed vaccination). In addition, about 1.8 million records were excluded, as they did not have the date of vaccination for BCG that is applied in Colombia at the time of birth, as stipulated by EIP, which could overestimate the timeliness for applications in those that were included and that it is probably related to difficulties in the initial registration of the vaccine in hospital birth care centers and the subsequent issuance of the vaccination card when the child is taken to vaccination centers close to their places of residence. Due to its observational and retrospective nature, it is possible that confounding factors could not have been identified, even from the origin of the data. There are also important strengths, especially due to the large amount of data collected over 6 years for more than 3 million children from all regions of the country which, through a Big Data analysis also allowing their differentiation by regime of affiliation to the health system and by ethnic group.

Conclusions

The vaccination timeliness of the EIP of Colombia is high, with proportions of 72–96% for most vaccines (exceptions: seasonal influenza and yellow fever), which helps achieving good protection against preventable infections. Differences between groups were identified, mainly the lower timeliness rate among indigenous people, which make it necessary to propose improvement strategies that will guarantee the immunization of the entire child population of the country.

Supplementary Material

Supplemental Material

Jorge Enrique Machado-Alba is a physician, Doctor in Pharmacology with 20 years of experience in research and more than 30 years in university teaching. He founded and leads the research group in Pharmacoepidemiology and Pharmacovigilance, which is endorsed and recognized by the Ministry of Science and Technology of Colombia in category A1 (https://scienti.minciencias.gov.co/gruplac/welcome/login_success.do). The research group is dedicated to conducting studies on the use of medications, to identify the results of pharmacological interventions in Colombia, their effectiveness, safety, appropriate and inappropriate uses. They have more than 240 publications (about 167 in PubMed) and are a national reference on pharmacology and pharmacoepidemiology.

Disclosure statement

JCVZ is a Sanofi employee and may hold shares and stock options in the company; JMA, AGM and MMD have no conflict of interest.

Author contributions

Conceptualizacion: JEMA and MEMD.

Methodology: JEMA, MEMD and JCVZ

Validation: JEMA, AGM and MEMD

Formal analysis: JEMA, AGM and MEMD

Investigation: JEMA, MEMD and JCVZ

Data curation: JEMA, AGM and MEMD

Writing original draft: JEMA and MEMD

Resources: JCVZ

All authors contributed to the writing of the manuscript and the revised drafts.

We do not use AI-assisted technologies.

All authors had access and verified the data. Jorge Machado-Alba is responsible for submitting the manuscript to the journal.

Data availability statement

Data access: DOI: dx.doi.org/10.17504/protocols.io.n2bvj3k9nlk5/v1.

Institutional review board statement

All personal information was handled with strict confidentiality, and never had data that could lead to patient identification. The protocol was classified according to Resolution 8430/of 1993 of the Ministry of Health as a non-risk Research. The ethical principles of justice, non-maleficence, beneficence, and confidentiality established by the Declaration of Helsinki were respected. No personal data of any of the subjects were considered. The protocol obtained approval from the bioethics committee of the Universidad Tecnológica de Pereira (Approval code: 01-14-12-20).

Supplementary material

Supplemental data for this article can be accessed on the publisher’s website at https://doi.org/10.1080/21645515.2024.2395685
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