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Allergic reactions to the Ad26.COV2.S Vaccine in South Africa
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  • Jonny PETER,
  • Cascia Day,
  • Simbarashe Takuva,
  • Azwidihwi Takalani,
  • Imke Engelbrecht,
  • Nigel Garrett,
  • Ameena Goga,
  • Vernon Louw,
  • Jessica Opie,
  • Barry Jacobson,
  • Ian Sanne,
  • Linda Gail-Bekker,
  • Glenda Gray
University of Cape Town Division of Immunology

Corresponding Author:[email protected]

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Cascia Day
University of Cape Town Division of Immunology
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Simbarashe Takuva
University of Pretoria School of Health Systems and Public Health
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Azwidihwi Takalani
Fred Hutchinson Cancer Research Center
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Imke Engelbrecht
Right to Care
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Nigel Garrett
Centre for the Aids Programme of Research in South Africa
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Ameena Goga
University of Pretoria
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Vernon Louw
Division of Clnical Haematology Department of Medicine Faculty of Health Sciences University of Cape Town and Groote Schuur Hospital Cape Town South Africa
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Jessica Opie
University of Cape Town Department of Pathology
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Barry Jacobson
University of the Witwatersrand Faculty of Health Sciences
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Ian Sanne
Right to Care
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Linda Gail-Bekker
Desmond Tutu HIV Foundation
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Glenda Gray
South African Medical Research Council Durban
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Abstract ( n=254/250 words)   Background: The Janssen-Ad26.COV2.S vaccine is authorised for use in several countries with more than 30 million doses administered. Mild and severe allergic adverse events following immunisation(AEFI) have been reported. The aim of this report is 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 477234 South African Healthcare Workers between 17 February and 17 May 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 (BCC) and NIAID case definitions.  Results: A large cohort of South African healthcare workers received the Ad26.COV2.S vaccination. Only 250(0.052%) patients reported any allergic-type reaction(less than 1 in 2000), with four cases of adjudicated anaphylaxis (BCC level 1, n=3)(prevalence of 8.4 per million doses). All anaphylaxis cases had a prior history of drug or vaccine-associated anaphylaxis. Cutaneous allergic reactions were the commonest non-anaphylatic reactions and included: self-limiting, transient/localised rashes requiring no healthcare contact(n=91); or isolated urticaria and/or angioedema[n=70 median  onset 48(IQR 11.5-120) hours post vaccination] that necessitated healthcare contact(81%), antihistamine(63%), and/or systemic/topical corticosteroid(16%). All immediate (including adjudicated anaphylaxis) and the majority of delayed AEFI(65/69) cases resolved completely.   Conclusions: Allergic AEFI are rare following a single-dose of Ad26.COV with complete resolution in  all cases of anaphylaxis. Though 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.   Keywords: allergic reaction, anaphylaxis, COVID19 adenovirus vaccine; Janssen-Ad26.COV2.S vaccine, urticaria