
==== Front
Int J Hematol Oncol Stem Cell Res
Int J Hematol Oncol Stem Cell Res
IJHOSCR
International Journal of Hematology-Oncology and Stem Cell Research
2008-3009
2008-2207
Tehran University of Medical Sciences, Hematology-Oncology and Stem Cell Transplantation Research Center Tehran, Iran

10.18502/ijhoscr.v18i3.16111
IJHOSCR-18-297
Review Article
Aplastic Anemia Following COVID-19 Vaccination: A Systematic Review of Case Reports and Case Series
Cahuapaza-Gutierrez Nelson Luis 12
Campos-Escalante Tsuriel Sofía 1
1 Facultad de Ciencias de la Salud, Carrera de Medicina Humana, Universidad Científica Del Sur, Lima, Perú
2 Change Research Working Group, Universidad Científica del Sur, Lima, Perú
Corresponding Author: Nelson Luis Cahuapaza-Gutierrez, Facultad de Ciencias de la Salud, Carrera de Medicina Humana, Universidad Científica Del Sur, Lima, Perú. E-mail: 100065659@cientifica.edu.pe
1 7 2024
18 3 297305
6 5 2023
23 12 2023
Copyright © 2024 Tehran University of Medical Sciences.
https://creativecommons.org/licenses/by-nc/4.0/ This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International license (https://creativecommons.org/licenses/by-nc/4.0/). Non-commercial uses of the work are permitted, provided the original work is properly cited.
Background: Aplastic anemia (AA) is the prototypical bone marrow failure syndrome due to the destruction of hematopoietic stem cells by cytotoxic T cells. According to case reports, vaccines could lead to the development of AA. We conducted the present systematic review to evaluate cases of AA following vaccination against coronavirus disease (COVID-19).

Materials and Methods: We searched the following databases: PubMed, Scopus, and EMBASE in English, Portuguese, and Spanish languages until April 24, 2023. Published reports and case series on AA following vaccination against COVID-19 were included. The Joanna Brigs Institute (JBI) was used to assess study quality and risk of bias.

Results: Six studies were selected from 102 research studies, and data were extracted according to the inclusion criteria. All case reports and case series reported the occurrence of AA following COVID-19 vaccination. AA events were mainly observed in vaccines with messenger ribonucleic acid technology (Moderna; Pfizer-BioNTech). AA was diagnosed by bone marrow biopsy, and severity was determined by Camitta criteria.

Conclusion: All cases of AA were properly diagnosed. The sample size was small; therefore, further investigations are required to demonstrate and elucidate the complete pathophysiological mechanisms of AA development after receiving COVID-19 vaccination.

Key Words

Anemia
Aplastic
Aplastic anemia
COVID-19 Vaccines
SARS-CoV-2 Vaccines
==== Body
pmcIntroduction

Aplastic anemia (AA) is a rare hematologic disorder presenting as a bone marrow failure syndrome1. It has an estimated incidence in Europe and the USA of 2 to 3 cases/million and 5 to 6 cases/million in Asia, with a bimodal distribution for age between 15-25 years and over 60 years, with no gender and race differences2.

Aplastic anemia has diverse etiologies; the common causes of aplastic anemia are occupational exposure to haptens, such as benzene and pesticides, and medication exposure, such as chloramphenicol and antiepileptics3.

AA is also associated with pregnancy, although it is a rare condition, but if left untreated, it can cause severe maternal and fetal complications4. Other causes include hepatitis, viral infections, radiation, and autoimmune disorders5. In most cases of AA, the cause is unknown, so it is called idiopathic AA6.

Acquired AA is immune-mediated by cytotoxic T cells that destroy and suppress hematopoietic progenitor cells. Hereditary AA is caused by various germline mutations involving alterations in DNA repair, telomere maintenance, or hematopoiesis7. Patients with AA usually have anemia, thrombocytopenia, and infections resulting from autoimmune destruction. A hemoglobin (Hb) concentration <100 g/L, platelet count (PLT) <50 × 10 9 /L, and neutrophil count (ANC) <1.5 × 10 9 /L must be present for the diagnosis of AA. The Camitta criteria are used to assess the severity of AA and divide it into three groups: non-severe AA (NSAA), severe AA (SAA), and very severe AA (VSAA)8. Treatment for AA is based on immunosuppressive therapy (IST) (anti-thymocyte globulin (ATG) and cyclosporin A (CsA)) or stem cell transplantation. IST has a hematologic response rate of about 60 to 65%. However, eltrombopag (EPAG), a thrombopoietin-receptor agonist, can improve the response9.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causing coronavirus disease (COVID-19) continues, with new variants spreading rapidly and causing high morbidity and mortality, with more than 763 million diagnosed cases and more than 6.9 million deaths worldwide10,11. Faced with the emerging status of COVID-19, the US Food and Drug Administration (FDA) issued the emerging use of vaccines such as Pfizer-BioNTech (BNT162b2 mRNA), modern (mRNA-1273) and Janssen/Johnson (traditional viral vector)9. SARS-CoV-2 vaccines include inactivated, live attenuated, viral vector, protein subunit, RNA, DNA, and virus-like particles. The vaccines are intended to elicit T-cell immunity, B-cell immunity, and other immune responses12.

Case reports have reported the occurrence of AA after vaccination against SARS-CoV-2, possibly related to the immune response that the vaccines produce13-15. AA has been reported as an adverse event after vaccination; hence, it is essential to synthesize the current evidence to know this adverse reaction. Therefore, our objective was to systematically review of all published case reports and case series of AA after receiving the COVID-19 vaccine.

MATERIALS AND METHODS

The present systematic review follows the guidelines of "Preferred Reporting Items for Systematic Reviews and Meta-Analyses" (PRISMA)16.

Review objectives

The main objective of the present systematic review is to clarify the possible relationship of aplastic anemia associated with COVID-19 vaccination.

Search strategy

For the present review, a selective bibliographic search was performed in the following electronic databases: PubMed, Scopus, and EMBASE. A search strategy was created with the term "Aplastic anemia" related to the terms "COVID-19 Vaccines" and "SARS-CoV-2 Vaccines" using Boolean operands "AND" or "OR". The search was completed with gray literature using the following search string: "Aplastic anemia" AND "COVID-19 Vaccine" in Google Scholar. In addition, the reference list of included articles was manually reviewed to identify additional studies. The search strategy for each database is detailed in Supplementary Material. The search was limited to English, Portuguese, and Spanish. The first search was conducted on April 6, 2023, followed by an additional search on April 24, 2023.

The search strategy follows the guidelines of the "Preferred Reporting Items for Systematic Reviews and Meta-Analyses literature search extension" (PRISMA-S)17.

Criteria for inclusion and exclusion

Case reports and case series studies on aplastic anemia following COVID-19 vaccination were included. Systematic review and narrative studies, letters to the editor, animal studies, hypotheses, and in vitro studies were excluded. In addition, articles with insufficient data and written in languages other than English, Portuguese, and Spanish were excluded.

Study selection

The author (NLCG) downloaded all references from the databases to an EndNote document to remove duplicate items. Then, the author exported all references to the Rayyan QCRI website (https://rayyan.qcri.org/). Two authors (NLCG and TSCE) independently screened the titles and abstracts of the references to identify relevant studies that met the inclusion criteria for eligibility. The reviewers then evaluated the selected studies in full text. Any discrepancies between reviewers were resolved by mutual discussion.

Data extraction

Two authors (NLCG and TSCE) independently extracted the data of interest. Any disagreement was resolved by mutual discussion. Extraction was performed using a previously prepared Microsoft Excel sheet. Data such as the author's name, year of publication, age, sex, type of vaccine, history, time after vaccination, clinical manifestations, laboratory, biopsy, disease severity, treatment, and evolution were extracted. The characteristics of the studies are detailed in Table 1.

Quality Evaluation

To assess the quality and risk of bias of the present systematic review, the Joanna Brigs Institute (JBI)18 was used. All studies were assessed by the NLCG author, and any disagreements were mutually resolved. The JBI presents four available assessment options: "Yes, No, Unclear, and Not applicable". In addition, affirmative responses were summarized from 0 to 8. Articles with a score below 4 are considered low quality and those above 4 are considered high quality. The evaluation of the included studies is detailed in Tables 2 and 3.

Results

Eligible studies

A total of 102 studies were identified. After the elimination of duplicates and evaluation for eligibility, 9 articles were selected. Finally, 7 studies were used in the present systematic review. The study selection process is shown in the PRISMA 2020 flow chart Figure 1.

Characteristics of studies included

Six studies were included for systematic review (5 case reports, 1 case series). Nine patients were included in this analysis. The mean age of patients who developed AA following COVID-19 vaccination was 59.1 years. The gender distribution was (2 females, 7 males). Two patients had a history; the first had Hashimoto's thyroiditis and pneumococcal and influenza vaccination, and the second had thalassemia. AA events were mostly observed after receiving the Moderna (mRNA) vaccine (after the first dose, n=1; after the second dose, n=3), followed by the Pfizer BioNTech (mRNA) vaccine (after the first dose, n=1; after the second dose, n=2) and finally the Oxford-AstraZeneca (viral vector) vaccine (after the first dose, n=1; after the second dose, n=1). The onset of symptoms after receiving vaccination was estimated to be mainly 2 weeks (n=4), the minimum time was 1 day and the maximum 1 month. The clinical manifestations reported were bleeding, hematomas, fever, dyspnea, muscle pain, melena, petechiae, and asthenia. Regarding laboratory parameters, the most affected series was Platelets (PLT) (Range: 1-15x10 9 /l), followed by hemoglobin (Hb) (Range: 43-112 g/l) and absolute neutrophil count (ANC) (Range: 0-0.99x10 9 /l). Diagnosis was made by bone marrow biopsy, and Hypocellularity (<15%) was observed in all cases. The severity of AA was determined by Camitta criteria with VSAA (n=4), SAA (n=4) and NSAA (n=1). Patients received IST + EPAG (n=4), IST + EPAG + methylprednisolone (n=2), IST (n=1), Alo-HCST (n=1) and CsA alone (n=1). Only one patient receiving IST + EPAG + methylprednisolone was switched to HCST. Most patients, except one readmitted for neutropenic fever and pneumonia, had a favorable evolution. The characteristics of the studies are detailed in Table 1.

Table 1 Characteristics of reported studies on the development of aplastic anemia after vaccination against SARS-CoV-2

Author	Year of publication	Patient age (years)	Sex	Vaccine type	Background	Symptom onset after vaccination	Clinical manifestations	Laboratory	Bone marrow biopsy	Severity of aplasia (According to Camitta Criteria)	Main treatment	Evolution	
Cecchi et al.19	2021	76	M	Pfizer-BioNTech (ARNm)	None	1 month after second dose	Asthenia and mucocutaneous bleeding	PLT: 3x10 9 /l
WBC: 3.7x10 9 /l
ANC: 0.46x10 9 /l
Hb: 112 g/l	Hypocellularity 10%	SAA	IST	Unknown	
Tabata et al.13	2021	56	M	Pfizer-BioNTech (ARNm)	None	4 days after second dose	Bleeding in oral cavity	PLT: 11x10 9 /l
WBC: 1.6x10 9 /l	Hypocellularity	VSAA	Alo-HCST	Favorable	
Wang et al.20	2022	67	F	Modern (ARNm)	Hashimoto's thyroiditis, pneumococcal and seasonal influenza vaccines	2 weeks after second dose	None	PLT: 3x10 9 /l
WBC: 1.8x10 9 /l
ANC: 0.31x10 9 /l
Hb: 45 g/l	Hypocellularity 5%	SAA	IST + EPAG	Favorable	
Sridhara et al.21	2022	60	M	Modern (ARNm)	None	1 day after second dose	Hematomas and epistaxis	PLT: 1x10 9 /l
WBC: 1.2x10 9 /l
ANC: 0x10 9 /l
Hb: 80 g/l	Hypocellularity < 5%	VSAA	IST + methylprednisolone + EPAG	Discharged, readmitted two days later for neutropenic fever and pneumonia.	
Woo et al.14	2022	53	M	Modern (ARNm)	None	2 weeks after first dose	Hematomas and melena	PLT: 2x10 9 /l
WBC: 1.92x10 9 /l
ANC: 0.12x10 9 /l
Hb: 66 g/l	Hypocellularity < 5%	VSAA	IST + EPAG	Favorable	
Chen et al.15	2022	64	F	Oxford-AstraZeneca (viral vector)	None	5 days after first dose	Petechiae and fever	PLT: 3x10 9 /l
ANC: 0.99x10 9 /l
Hb: 78 g/l	Hypocellularity < 3%	VSAA	IST + methylprednisolone + EPAG; HCST	Favorable	
73	M	Modern (ARNm)	None	2 weeks after second dose	Fever, muscular pain, and dyspnea	PLT: 13x10 9 /l
ANC: 0.499x10 9 /l
Hb: 79 g/l	Hypocellularity < 5%	SAA	IST + EPAG	Favorable	
64	M	Oxford-AstraZeneca (viral vector)	None	2 weeks after second dose	None	PLT: 15x10 9 /l
ANC: 0.747x10 9 /l
Hb: 69 g/l	Hypocellularity 3-5%	NSAA	CsA	Partial response	
19	M	Pfizer-BioNTech (ARNm)	Thalassemia	3 weeks after first dose	Severe dyspnea on exertion	PLT: 11x10 9 /l
ANC: 0.281x10 9 /l
Hb: 43 g/l	Hypocellularity 10-15%	SAA	IST + EPAG	Partial response	
M: male; F: female; mRNA: messenger ribonucleic acid; PLT: platelets; WBC: white blood cells; ANC: absolute neutrophil count; Hb: hemoglobin; IST: immunosuppressive therapy; Alo-HCST: allogeneic hematopoietic stem cell transplantation; EPAG: eltrombopag; CsA: cyclosporin-A; GAT: antithymocyte globulin; G-CSF: granulocyte colony-stimulating factor; G-CSF: granulocyte colony-stimulating factor.

NSAA: non-severe aplastic anemia; SAA: severe aplastic anemia; VSAA: very severe aplastic anemia

Table 2 Quality assessment based on the JBI tool for case reports

	Cecchi et al.	Tabata et al.	Wang et al.	Sridhara et al.	Woo et al.	
8. Does the case report
provide takeaway lessons?	Yes	Yes	Yes	Yes	Yes	
1. Were patient’s
demographic characteristics
clearly described?	Yes	Yes	Yes	Yes	Yes	
2. Was the patient’s history
clearly described and
presented as a timeline?	Yes	Yes	Yes	Yes	Yes	
3. Was the current clinical
condition	Yes	Yes	Yes	Yes	Yes	
4. Were diagnostic tests or
assessment methods and
the results clearly
described?	Yes	Yes	Yes	Yes	Yes	
5. Was the intervention(s) or
treatment procedure(s)
clearly described?	Yes	Yes	Yes	Yes	Yes	
6. Was the post-intervention
clinical condition clearly
described?	Unclear	Yes	Yes	Yes	Yes	
7. Were adverse events
(harms) or unanticipated
events identified and
described?	Yes	Yes	Yes	Yes	Yes	

Table 3 Quality assessment based on the JBI tool for case series

	Chen et al.	
1. Were there clear criteria for
inclusion in the case series?	Yes	
2. Was the condition measured in a
standard, reliable way for all
participants included in the case
series?	Yes	
3. Were valid methods used for
identification of the condition for all
participants included in the case
series?	Yes	
4. Did the case series have
consecutive inclusion of participants?	Yes	
5. Did the case series have complete
inclusion of participants?	Yes	
6. Was there clear reporting of the
demographics of the participants in
the study?	Yes	
7. Was there clear reporting of clinical
information of the participants?	Yes	
8. Were the outcomes or follow up
results of cases clearly reported?	Yes	
9. Was there clear reporting of the
presenting site(s)/clinic(s)
demographic information?	Yes	
10. Was statistical analysis appropriate?	Yes	
Overall appraisal:	10 out of 10	

Figure 1 Flow diagram of study selection process for this review

Discussion

Through the present systematic review, we found that vaccination against COVID-19, mainly those with mRNA technology, mainly the Modern vaccine. Most cases occurred in male patients. With severity classification according to SAA and VSAA criteria, only one case reported NSAA. Most of the patients presented a favorable evolution and response to treatment. According to JBI the quality assessment of studies included in this review was of high quality.

Vaccinations and aplastic anemia

The speed of vaccination against COVID-19 generated many concerns in the clinical setting regarding the safety of the various vaccines. Given this, several diseases were reported as complications of vaccination, mainly cardiac complications such as myocarditis, pericarditis, and acute myocardial infarction22. Hematological complications include autoimmune disorders, such as immune thrombotic thrombocytopenic purpura, autoimmune hemolytic anemia, Evans syndrome, and vaccine-induced thrombotic thrombocytopenia23-26. In addition, very rare diseases, such as atypical hemolytic uremic syndrome, have been reported27.

The current evidence we have for vaccines is from the various clinical trials. The messenger ribonucleic acid (mRNA) technology vaccines were associated with a higher risk of adverse events. However, in the risk/benefit ratio, all types of vaccines outweigh the risks of these vaccines, and it is highly recommended28. Our study showed a relationship with mRNA technology vaccines, mainly Modern. The occurrence of post-vaccination AA is not new. Previously, rare cases have been described about other types of vaccines, such as the occurrence of AA after receiving varicella zoster and H1N1 influenza vaccine29,30. A retro-prospective observational analysis by Röth et al. showed that vaccination against COVID-19 generated relapse in patients with AA who were in stable hematologic remission. The vaccine used was Pfizer-BioNTech (mRNA), and most cases occurred after the second dose31.

The main hypotheses involve molecular mimicry. The vaccine could contribute to the pathogenesis of AA13. Moreover, the underlying immune predisposition could have allowed the vaccines to trigger a cytotoxic T lymphocyte response producing AA21. Another hypothesis posits that the vaccine may induce aberrant T-cell activation15. All the hypotheses raised could contribute to the development of AA since in AA, there is immune dysregulation by expansion of cytotoxic T cells, decrease in regulatory T cells, and increase in TH-1 inflammation-related cytokines and proteins, particularly interferon-γ (IFN- γ), destroying hematopoietic stem cells9.

Limitations

Our review has some limitations, which include only the participation of reported case reports and case series. Therefore, the results should be interpreted with some caution. In addition, few studies were included.

CONCLUSION

We systematically evaluated all reported case reports and case series of AA after COVID-19 vaccination. Our systematic review is the first on this pathology of interest and provides an overview of the reported case reports and case series. Further studies are suggested to elucidate the complete pathophysiological mechanisms of the vaccine and the development of AA. Moreover, comparing the number of reported cases of AA with COVID-19 vaccine doses administered and the evolution of the patients is also recommended. We observed that the benefits of vaccination outweigh the risks. However, observation of patients with the clinical manifestations of AA is essential.

ACKNOWLEDGEMENTS

The main author would like to give a special thank you to his mother, Mrs. Frida Gutierrez Figueroa, for her constant support, motivation, and teaching during the research process.

CONFLICTS OF INTEREST

The authors declare no conflicts of interest.
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References

1 Brzeźniakiewicz-Janus K Rupa-Matysek J Gil L Acquired Aplastic Anemia as a Clonal Disorder of Hematopoietic Stem Cells Stem Cell Rev Rep 2020 16 3 472 81 32270433
2 Urbanowicz I Nahaczewska W Celuch B Narrative review of aplastic anemia—the importance of supportive treatment Ann Palliat Med 2021 10 1 694 699 33353360
3 Shallis RM Ahmad R Zeidan AM Aplastic anemia: Etiology, molecular pathogenesis, and emerging concepts Eur J Haematol 2018 101 6 711 20 30055055
4 Jaime-Pérez JC González-Treviño M Gómez-Almaguer D Pregnancy-associated aplastic anemia: a case-based review Expert Rev Hematol 2021 14 2 175 84 33430674
5 Sweeney R Esmail F Mirza KM Nand S Hypercellular bone marrow in aplastic anemia: A case report of two patients Clin Case Rep 2021 9 11 e04845 34853682
6 Durrani J Maciejewski JP Idiopathic aplastic anemia vs hypocellular myelodysplastic syndrome Hematology Am Soc Hematol Educ Program 2019 2019 1 97 104 31808900
7 Giudice V Selleri C Aplastic anemia: Pathophysiology Semin Hematol 2022 59 1 13 20 35491054
8 Killick SB Bown N Cavenagh J Dokal I Foukaneli T Hill A et  al Guidelines for the diagnosis and management of adult aplastic anaemia Br J Haematol 2016 172 2 187 207 26568159
9 Patel BA Townsley DM Scheinberg P Immunosuppressive therapy in severe aplastic anemia Semin Hematol 2022 59 1 21 9 35491055
10 WHO Coronavirus (COVID-19) Dashboard 2023 accessed 3 April 2023 Geneva World Health Organization Available at:https://data.who.int/dashboards/covid19/cases?n=c
11 Li M Wang H Tian L Pang Z Yang Q Huang T et  al COVID-19 vaccine development: milestones, lessons and prospects Signal Transduct Target Ther 2022 7 146 35504917
12 Ajmera K Bansal R Wilkinson H Goyal L Gastrointestinal Complications of COVID-19 Vaccines Cureus 2022 14 4 e24070 35573556
13 Tabata S Hosoi H Murata S Takeda S Mushino T Sonoki T Severe aplastic anemia after COVID-19 mRNA vaccination: Causality or coincidence? J Autoimmun. 2022 126 102782 34920343
14 Woo S Kim B Lee SC Kim MS Yoon YA Choi YJ Very severe immune aplastic anemia after mRNA vaccination against COVID-19 responds well to immunosuppressive therapy: clinical characteristics and comparison to previous reports Hematol Amst Neth 2022 27 1 1191 5
15 Chen CY Chen TT Hsieh CY Lien MY Yeh SP Chen CC Case reports of management of aplastic anemia after COVID-19 vaccination: a single institute experience in Taiwan Int J Hematol 2023 117 1 149 52 36057889
16 Page MJ McKenzie JE Bossuyt PM Boutron I Hoffmann TC Mulrow CD et  al The PRISMA 2020 statement: an updated guideline for reporting systematic reviews BMJ 2021 372 n71 33782057
17 Rethlefsen ML Kirtley S Waffenschmidt S Ayala AP Moher D Page MJ et  al PRISMA-S: an extension to the PRISMA Statement for Reporting Literature Searches in Systematic Reviews Syst Rev 2021 10 1 39 33499930
18 Lockwood C Munn Z Porritt K Qualitative research synthesis: methodological guidance for systematic reviewers utilizing meta-aggregation Int J Evid Based Healthc 2015 13 3 179 87 26262565
19 Cecchi N Giannotta JA Barcellini W Fattizzo B A case of severe aplastic anaemia after SARS‐CoV‐2 vaccination Br J Haematol 2022 196 6 1334 6 34783367
20 Wang X Laczko D Caponetti GC Rabatin S Babushok DV Severe aplastic anaemia after serial vaccinations for SARS‐CoV‐2, pneumococcus and seasonal influenza EJHaem 2022 3 3 983 8 35941884
21 Sridhara S Nair R Stanek M Severe Aplastic Anemia After Receiving SARS-CoV-2 Moderna mRNA Vaccination J Hematol 2022 11 1 34 9 35356634
22 Fazlollahi A Zahmatyar M Noori M Nejadghaderi SA Sullman MJM Shekarriz-Foumani R et  al Cardiac complications following mRNA COVID-19 vaccines: A systematic review of case reports and case series Rev Med Virol 2022 32 4 e2318 34921468
23 Mingot-Castellano ME Butta N Canaro M Gómez del Castillo Solano M del C Sánchez-González B Jiménez-Bárcenas R et  al COVID-19 Vaccines and Autoimmune Hematologic Disorders Vaccines 2022 10 6 961 35746569
24 Fatima Z Reece BRA Moore JS Means RT Autoimmune Hemolytic Anemia After mRNA COVID Vaccine J Investig Med High Impact Case Rep. 2022 10 23247096211073256
25 Gadi SRV Brunker PAR Al-Samkari H Sykes DB Saff RR Lo J et  al Severe autoimmune hemolytic anemia following receipt of SARS-CoV-2 mRNA vaccine Transfusion 2021 61 11 3267 71 34549821
26 Hidaka D Ogasawara R Sugimura S Fujii F Kojima K Nagai J et  al New-onset Evans syndrome associated with systemic lupus erythematosus after BNT162b2 mRNA COVID-19 vaccination Int J Hematol 2022 115 3 424 7 34687421
27 Rysava R Peiskerova M Tesar V Benes J Kment M Szilágyi Á Atypical hemolytic uremic syndrome triggered by mRNA vaccination against SARS-CoV-2: Case report Front Immunol 2022 13 1001366
28 Kouhpayeh H Ansari H Adverse events following COVID-19 vaccination: A systematic review and meta-analysis Int Immunopharmacol. 2022 109 108906 35671640
29 Angelini P Kavadas F Sharma N Richardson SE Tipples G Roifman C et  al APLASTIC ANEMIA FOLLOWING VARICELLA VACCINE Pediatr Infect Dis J 2009 28 8 746 19633522
30 Donnini I Scappini B Guidi S Longo G Bosi A Acquired severe aplastic anemia after H1N1 influenza virus vaccination successfully treated with allogeneic bone marrow transplantation Ann Hematol 2012 91 3 475 6 21681390
31 Röth A Bertram S Schroeder T Haverkamp T Voigt S Holtkamp C Acquired aplastic anemia following SARS‐CoV‐2 vaccination Eur J Haematol 2022 109 2 186 94 35592930
