BACKGROUND : The Janssen-Ad26.COV2.S vaccine is authorized for use in several countries, with more than 30 million doses administered. Mild and severe allergic adverse events following immunization (AEFI) have been reported.
OBJECTIVE : We sought to detail allergic reactions reported during the Sisonke phase 3B study in South Africa.
METHODS : A single dose of the Ad26.COV2.S vaccine was administered to 4,77,234 South African health care workers between February 17 and May 17, 2021. Monitoring of adverse events used a combination of passive reporting and active case finding. Telephonic contact was attempted for all adverse events reported as “allergy.” Anaphylaxis adjudication was performed using the Brighton Collaboration and National Institute of Allergy and Infectious Disease case definitions.
RESULTS : Only 251 (0.052%) patients reported any allergic-type reaction (<1 in 2000), with 4 cases of adjudicated anaphylaxis (Brighton Collaboration level 1, n = 3) (prevalence of 8.4 per million doses). All anaphylaxis cases had a previous history of drug or vaccine-associated anaphylaxis. Cutaneous allergic reactions were the commonest nonanaphylatic reactions and included self-limiting, transient/localized rashes requiring no health care contact (n = 92) or isolated urticaria and/or angioedema (n = 70; median onset, 48 [interquartile range, 11.5-120] hours postvaccination) that necessitated health care contact (81%), antihistamine (63%), and/or systemic/topical corticosteroid (16%). All immediate (including adjudicated anaphylaxis) and most delayed AEFI (65 of 69) cases resolved completely.
CONCLUSIONS : Allergic AEFI are rare following a single dose of Ad26.COV, with complete resolution in all cases of anaphylaxis. Although rare, isolated, delayed-onset urticaria and/or angioedema was the commonest allergic AEFI requiring treatment, with nearly half occurring in participants without known atopic disease.The Sinsonke Study is funded by the South African Medical Research Council. J.P.’s
research is supported by a career development award and financial support from the National Institutes of Health; the European Developing Clinical Trials Partnership (EDCTP2 Program supported by the European Union; and the
SA Medical Research Council and National Research Foundation.https://www.sciencedirect.com/journal/journal-of-allergy-and-clinical-immunology-globalhj2023Paediatrics and Child HealthSchool of Health Systems and Public Health (SHSPH
