1. Safety and immunogenicity of booster vaccination and fractional dosing with Ad26.COV2.S or BNT162b2 in Ad26.COV2.S-vaccinated participants.
- Author
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Catherine Riou, Jinal N Bhiman, Yashica Ganga, Shobna Sawry, Frances Ayres, Richard Baguma, Sashkia R Balla, Ntombi Benede, Mallory Bernstein, Asiphe S Besethi, Sandile Cele, Carol Crowther, Mrinmayee Dhar, Sohair Geyer, Katherine Gill, Alba Grifoni, Tandile Hermanus, Haajira Kaldine, Roanne S Keeton, Prudence Kgagudi, Khadija Khan, Erica Lazarus, Jean Le Roux, Gila Lustig, Mashudu Madzivhandila, Siyabulela F J Magugu, Zanele Makhado, Nelia P Manamela, Qiniso Mkhize, Paballo Mosala, Thopisang P Motlou, Hygon Mutavhatsindi, Nonkululeko B Mzindle, Anusha Nana, Rofhiwa Nesamari, Amkele Ngomti, Anathi A Nkayi, Thandeka P Nkosi, Millicent A Omondi, Ravindre Panchia, Faeezah Patel, Alessandro Sette, Upasna Singh, Strauss van Graan, Elizabeth M Venter, Avril Walters, Thandeka Moyo-Gwete, Simone I Richardson, Nigel Garrett, Helen Rees, Linda-Gail Bekker, Glenda Gray, Wendy A Burgers, Alex Sigal, Penny L Moore, and Lee Fairlie
- Subjects
Public aspects of medicine ,RA1-1270 - Abstract
We report the safety and immunogenicity of fractional and full dose Ad26.COV2.S and BNT162b2 in an open label phase 2 trial of participants previously vaccinated with a single dose of Ad26.COV2.S, with 91.4% showing evidence of previous SARS-CoV-2 infection. A total of 286 adults (with or without HIV) were enrolled >4 months after an Ad26.COV2.S prime and randomized 1:1:1:1 to receive either a full or half-dose booster of Ad26.COV2.S or BNT162b2 vaccine. B cell responses (binding, neutralization and antibody dependent cellular cytotoxicity-ADCC), and spike-specific T-cell responses were evaluated at baseline, 2, 12 and 24 weeks post-boost. Antibody and T-cell immunity targeting the Ad26 vector was also evaluated. No vaccine-associated serious adverse events were recorded. The full- and half-dose BNT162b2 boosted anti-SARS-CoV-2 binding antibody levels (3.9- and 4.5-fold, respectively) and neutralizing antibody levels (4.4- and 10-fold). Binding and neutralizing antibodies following half-dose Ad26.COV2.S were not significantly boosted. Full-dose Ad26.COV2.S did not boost binding antibodies but slightly enhanced neutralizing antibodies (2.1-fold). ADCC was marginally increased only after a full-dose BNT162b2. T-cell responses followed a similar pattern to neutralizing antibodies. Six months post-boost, antibody and T-cell responses had waned to baseline levels. While we detected strong anti-vector immunity, there was no correlation between anti-vector immunity in Ad26.COV2.S recipients and spike-specific neutralizing antibody or T-cell responses post-Ad26.COV2.S boosting. Overall, in the context of hybrid immunity, boosting with heterologous full- or half-dose BNT162b2 mRNA vaccine demonstrated superior immunogenicity 2 weeks post-vaccination compared to homologous Ad26.COV2.S, though rapid waning occurred by 12 weeks post-boost. Trial Registration: The study has been registered to the South African National Clinical Trial Registry (SANCTR): DOH-27-012022-7841. The approval letter from SANCTR has been provided in the up-loaded documents.
- Published
- 2024
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