ABSTRACT
Introduction: Vaccines prevent severe disease, but to prevent viral transmission and lessen the risk of new variants emerging they need to also enhance mucosal protection. Intramuscular (IM) vaccines induce systemic antibody and appear to transiently reduce transmission, but their effect on nasal antibody in previously infected subjects has not been studied. Aim(s): To study durability of local and systemic antibody responses after COVID-19 in those subsequently vaccinated. Method(s): Nasal fluid and plasma were collected from 448 hospitalised COVID-19 cases during admission and convalescence via the ISARIC4C/PHOSP-COVID studies. IgA/G to wildtype SARS-CoV-2 S, NP and to receptor binding domain (RBD) of Delta and Omicron variants were measured by ELISA. Result(s): Nasal IgA/G anti-S/RBD responses appeared within 28 days and remained high for 1 year(figure 1). Plasma IgA/G responses to S also remained elevated at 1 year(P<0.001). 87% of those with complete data were vaccinated between 6-12 months after infection;when nasal and plasma anti-NP IgA/G waned, whilst anti-S/RBD responses to Delta and Omicron were maintained or increased. Conclusion(s): This is the first study to demonstrate that IM vaccination may boost nasal antibody 1 year after COVID19. This may explain why IM vaccination reduces transmission, adding to the evidence for booster vaccines in COVID-19 recoverees. (Figure Presented).