Immunogenicity of BNT162b2 vaccine booster against SARS-CoV-2 Delta and Omicron variants in nursing home residents: A prospective observational study in older adults aged from 68 to 98 years
Enagnon Kazali Alidjinou, Julie Demaret, Bénédicte Corroyer-Simovic, Julien Labreuche, Anne Goffard, Jacques Trauet, Daniela Lupau, Sophie Miczek, Fanny Vuotto, Arnaud Dendooven, Dominique Huvent‐Grelle, Juliette Podvin, Daniel Dreuil, Karine Faure, Dominique Deplanque, Laurence Bocket, Alain Duhamel, Annie Sobaszek, Didier Hober, Michael Hisbergues, François Puisieux, Brigitte Autran, Yazdan Yazdanpanah, Myriam Labalette, Guillaume Lefèvre
Abstract
The present study aimed to evaluate the persistent immunogenicity offered by a third dose of BNT162b2 against Delta and Omicron variants, in nursing home (NH) residents. In this monocenter prospective observational study, anti-spike IgG levels, S1 domain reactive T cell counts, serum neutralizing antibody titers against Delta and Omicron variants were compared before and up to three months after the BNT162b2 booster dose, in NH residents without COVID-19 (COVID-19 naive) or with COVID-19 prior to initial vaccination (COVID-19 recovered). 106 NH residents (median [interquartile range] age: 86·5 [81;91] years) were included. The booster dose induced a high increase of anti-spike antibody levels in all subjects (p < 0.0001) and a mild transient increase of specific T cells. Before the booster dose, Delta neutralization was detected in 19% (n = 8/43) and 88% (n = 37/42) of COVID-19 naive and COVID-19 recovered subjects, respectively. Three months after the booster dose, all NH residents developed and maintained a higher Delta neutralization (p < 0·0001). Before the booster dose, Omicron neutralization was detected in 5% (n = 2/43) and 55% (n = 23/42) of COVID-19 naive and COVID-19 recovered subjects, respectively, and three months after, in 84% and 95%, respectively. Neutralizing titers to Omicron were lower than to Delta in both groups with a 35-fold reduction compared to Delta. The booster dose restores high neutralization titers against Delta in all NH residents, and at a lower level against Omicron in a large majority of participants. Future studies are warranted to assess if repeated BNT162b2 booster doses or new specific vaccines might be considered for protecting such fragile patients against Omicron and/or future SARS-CoV-2 variants. French government through the Programme Investissement d'Avenir (I-SITE ULNE/ANR-16-IDEX-0004 ULNE) and the Label of COVID-19 National Research Priority (National Steering Committee on Therapeutic Trials and Other COVID-19 Research, CAPNET).