Vaccines that elicit mucosal immune responses against SARS-CoV-2 could potentially be of exceptional importance in providing first line defense at the site of viral entry. The serological antibody response induced by SARS-CoV-2 vaccines have already been well characterized. In order to understand the mucosal immune response profiles of SARS-CoV-2 vaccines, we examined both the mucosal and systemic responses of subjects vaccinated by two different vaccination platforms: mRNA (Comirnaty) and inactivated virus (CoronaVac). Serial nasal epithelial lining fluid (NELF) and peripheral blood samples were collected in ten subjects who had received CoronaVac and thirty-two subjects who had received Comirnaty. We quantified IgA and IgG specific to SARS-CoV-2 S1 protein by ELISA in NELF and plasma samples. The neutralization effect of these two sample types were evaluated by surrogate ACE-SARS-CoV-2 Spike protein ELISA. Only Comirnaty induced nasal SARS-CoV-2 S1 protein-specific (S1-specific) IgA and IgG responses, which were evident as early as on 14 days after the first dose. The NELF samples of 72% of subjects became IgA+IgG+, while in 62.5% of subjects the samples were neutralizing by 7 days after the second dose. In 45% of the subjects their NELF remained neutralizing 50 days after the booster of Comirnaty. In plasma, 91% and 100% Comirnaty subjects possessed S1-specific IgA+IgG+ on 14 days after the first dose and 7 days after booster, respectively. The plasma collected on 7 days after booster was 100% neutralizing. The induction of S1-specific antibody by CoronaVac was IgG dominant, and 70% of the subjects possessed S1-specific IgG by 7 days after booster and were all neutralizing. This study reveals that Comirnaty is able to induce S1-specific IgA and IgG response with neutralizing activity in the nasal mucosa in addition to a consistent systemic response. The clinical implications and the biological mechanism of an additional nasal immune response induced by vaccines such as Comirnaty warrant further investigation.
Study on the mucosal and serological immune response to the Novel Coronavirus (SARS-CoV-2) vaccine