Hybrid humoral immune response of Pacific Islanders to BNT162b2 vaccination and Delta/Omicron infection: a cohort study

Background Pacific Islanders are underrepresented in vaccine efficacy trials. Few studies describe their immune response to COVID-19 vaccination. Yet, this characterization is crucial to re-enforce vaccination strategies adapted to Pacific Islanders singularities. Methods We evaluated the humoral immune response of 585 adults self-declaring as Melanesians, Europeans, Polynesians or belonging to other communities to Pfizer BNT162b2 vaccine. Anti-Spike and anti-Nucleoprotein IgG levels, capacity to neutralize SARS-CoV-2 variants and capacity to mediate Antibody-Dependent Cellular Cytotoxicity (ADCC) were assessed across communities at one and three months post-second dose or one and six months post-third dose. Results 61.3% of the sera tested contained anti-Nucleoprotein antibodies, evidencing mostly a hybrid immunity resulting from vaccination and SARS-CoV-2 infection. Anti-Spike IgG levels and capacity to mediate Omicron neutralization and ADCC were equivalent across the four ethnic communities at one-month post-immunization, during follow-up and at six months post-third dose, regardless of the infection status. Obese individuals (BMI>30 kg/m²) had significantly higher anti-Spike IgG levels at one-month post-immunization (+0.26 (0.04; 0.48) AU in LuLISA assay, p value = 0.017). Odds of Omicron neutralization at six months after the third dose decreased significantly in the 40-64 years and >=65 years groups (OR (95% CI) 0.48 (0.24-0.90) and 0.29 (0.14-0.58) respectively, p-value = 0.003). Conclusions Our study evidenced Pacific Islander’s robust humoral immune response to Pfizer BNT162b2 vaccine, which is pivotal to re-enforce vaccination deployment in a population at risk for severe COVID-19 (clinicaltrials.gov:NCT05135585).