mRNA vaccine boosts the SARS-CoV-2 specific mucosal antibody in recipients of inactivated and mRNA vaccines

ABSTRACT

Background: Little is known about the induction of mucosal Ab after the 3rd dose. We reported that two doses of BNT162b2 induced mucosal Abs as early as 14-days after the 1st dose. As BNT162b2 only provides the RNA encoding a full-length spike (S) protein, a mixed-vaccine regime with a vaccine that provides inactivated but intact viral particles was executed in some countries to expand the diversity of SARS-CoV-2 Abs. Aim and objectives: To examine the mucosal and plasma Ab induction in vaccine recipients receiving their 3rd vaccine dose with single or mixed vaccine type. Method(s) 46 healthy subjects who had BNT162b2 (B) or CoronaVac (C) in a sequence of either BBB, BBC, CCC or CCB were recruited for a longitudinal sampling of nasal fluid and blood. The S1-specific Ab and neutralizing Ab against SARS-CoV-2 VOCs were measured. Result(s) All BBB recipients (n=28) had nasal specific S1-IgA and IgG after two doses, and the Abs lasted six months and were readily induced after the 3rd dose. In BBC recipients (n=4), though they had prior induction of nasal Abs after two doses of B, the inactivated vaccine did not boost their nasal Abs. In CCC recipients (n=5), there was no induction on nasal Abs. If they adopted the CCB regime (CCB, n=11), they acquired nasal Ab after the 3rd dose. The nasal neutralizing antibodies against the wild type were boosted in 20/28 of the BBB recipients and induced in 8/11 of the CCB recipients but not in CCC or BBC recipients. Lastly, all 46 subjects had a boosted specific S1-IgA and S1IgG in plasma. Conclusion(s) Our findings highlighted the uniqueness of BNT162b2 in induing nasal Ab regardless of the vaccination history.