Pre-existing Igg antibodies to Hcovs Nl63 and Oc43 spike increased during the pandemic and after Covid-19 vaccination

Pre-existing immunity is associated with increased protection against SARS-CoV-2. There is little information regarding endemic human coronaviruses (HCOVs) from Pakistan. We investigated antibodies to SARS-CoV-2 and HCOVs NL63 and OC43, before and during the pandemic and determined the effect of COVID-19 vaccinations. We measured IgG to Spike proteins of SARS-CoV-2 in sera from pre-pandemic and post-pandemic periods (HC 2021). A psuedotyped virus assay was used to investigate serum neutralizing activity. We also measured IgG to SARS-CoV-2, HCoV-NL63 and HCoV-OC43 after individuals received either inactivated (Sinovac), or mRNA (BNT162b2), following up to weeks. Pre-pandemic sera showed low levels of IgG antibodies to Spike SARS-CoV-2 as well as low neutralizing capacity. Anti-SARS-CoV-2 Spike increased in HC 2021 to 49% seropositivity with equivalent neutralization capacity. Antibodies to IgG to HCoV-NL63 and HCoV-OC43 were higher in pandemic as compared with pandemic sera. IgG to Spike SARS-CoV-2 were positively correlated with HCoV-NL63 Spike only in pandemic sera, prior to vaccinations. Furthermore, SinoVac and BNT162b2 vaccinations both resulted in an increase in IgG antibodies to Spike SARS-CoV-2, HCoV-NL63 and HCoV-OC43. Pre-existing antibodies to endemic coronaviruses likely enhanced immunity in the population by driving cross reactive IgG antibodies, thereby enhancing protection against COVID-19.