Factors influencing adverse events following COVID-19 vaccination

Paola Villanueva, Ellie McDonald, Julio Croda, Mariana Garcia Croda, Margareth Dalcolmo, Glauce dos Santos, Bruno Jardim, Marcus Lacerda, David J. Lynn, Helen Marshall, Roberto D. Oliveira, Jorge Rocha, Alice Sawka, Fernando Val, Laure F. Pittet, Nicole L. Messina, Nigel Curtis

Research output: Contribution to journalArticlepeer-review


Various novel platform technologies have been used for the development of COVID-19 vaccines. In this nested cohort study among healthcare workers in Australia and Brazil who received three different COVID-19-specific vaccines, we (a) evaluated the incidence of adverse events following immunization (AEFI); (b) compared AEFI by vaccine type, dose and country; (c) identified factors influencing the incidence of AEFI; and (d) assessed the association between reactogenicity and vaccine anti-spike IgG antibody responses. Of 1302 participants who received homologous 2-dose regimens of ChAdOx1-S (Oxford-AstraZeneca), BNT162b2 (Pfizer-BioNTech) or CoronaVac (Sinovac), 1219 (94%) completed vaccine reaction questionnaires. Following the first vaccine dose, the incidence of any systemic reaction was higher in ChAdOx1-S recipients (374/806, 46%) compared with BNT162b2 (55/151, 36%; p = 0.02) or CoronaVac (26/262, 10%; p < 0.001) recipients. After the second vaccine dose, the incidence of any systemic reaction was higher in BNT162b2 recipients (66/151, 44%) compared with ChAdOx1-S (164/806, 20%; p < 0.001) or CoronaVac (23/262, 9%; p < 0.001) recipients. AEFI risk was higher in younger participants, females, participants in Australia, and varied by vaccine type and dose. Prior COVID-19 did not impact the risk of AEFI. Participants in Australia compared with Brazil reported a higher incidence of any local reaction (170/231, 74% vs 222/726, 31%, p < 0.001) and any systemic reaction (171/231, 74% vs 328/726, 45%, p < 0.001), regardless of vaccine type. Following a primary course of ChAdOx1-S or CoronaVac vaccination, participants who did not report AEFI seroconverted at a similar rate to those who reported local or systemic reactions. In conclusion, we found that the incidence of AEFI was influenced by participant age and COVID-19 vaccine type, and differed between participants in Australia and Brazil.

Original languageEnglish
Article number2323853
JournalHuman Vaccines and Immunotherapeutics
Issue number1
Publication statusPublished or Issued - 2024


  • adverse events
  • antibody responses
  • COVID-19 vaccine

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology
  • Pharmacology

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