Immunity post-COVID-19 recovery boosts the antibody immune response to SARS-CoV-2 vaccination

Measurement of strength and durability of SARS-COV-2 antibody response is important to understand the waning dynamics of immune response to both vaccines and infection. The study aimed to evaluate the level of IgG antibodies against SARS-CoV-2 and their persistence in recovered, naive and vaccinated individuals. We randomly investigate Anti-spike RBD IgG antibody responses in 10,000 individuals, both following infection with SARS-CoV-2 and immunization with SARS-COV-2 adenoviral-vector and killed vaccines. Overall, antibody titres in recovered vaccinated individuals and naive vaccinee persists beyond 20 weeks. The mean levels of anti-spike IgG antibodies were higher in vaccinated participants with prior COVID-19 infections than in individuals without prior infection. Decline for IgG antibodies were faster in vaccinated individuals without previous COVID-19 infection compared to those with previous COVID-19 infection. Vaccination with adenoviral-vector vaccines generates higher antibody titers than for killed virus vaccine. Slightly over half of asymptomatic unvaccinated individuals develops antibody response. Previous COVID-19 infection elicited robust and sustained levels of SARS-CoV-2 antibodies in vaccinated individuals. A single dose of the vaccine is likely to provide greater protection against SARS-CoV-2 infection in individuals with prior SARS-CoV-2 infection, than in SARS-CoV-2-naive individuals. This study also underlines that asymptomatic infection equally generates antibodies as symptomatic infection. Those vaccinated with inactivated vaccine may require more frequent boosters than those vaccinated with an adenoviral vaccine. These findings are important for formulating public health vaccination strategies during COVID-19 pandemic. ImportanceMeasurement of strength and durability of SARS-COV-2 antibody response is important to understand the waning dynamics of immune response to both vaccines and infection. We randomly surveyed 10,000 people for SARS-COV-2 antibodies. One vaccine dose with prior infection generated stronger immune response than two vaccine doses. Overall, antibody titres in recovered vaccinated individuals and naive vaccinee persists beyond 20 weeks. Vaccination with adenoviral-vector vaccines generates higher antibody titers than for killed virus vaccine slightly over half of asymptomatic unvaccinated individuals develops antibody response. This study emphasise on the benefit of vaccination in inducing strong immune response. These findings are important for formulating public health vaccination strategies during COVID-19 pandemic.