Antibody responses to known and unknown SARS-CoV-2 infections after mRNA vaccine booster

Abstract

We followed a fully-vaccinated (two mRNA vaccine doses) community cohort (n=41) without prior COVID-19 diagnosis from September 2021 through March 2022 through the Omicron wave following a booster mRNA vaccination. 19.5% of participants reported a known SARS-CoV-2 infection during the Omicron wave, which was confirmed by anti-nucleocapsid IgG. An additional 36.5% also developed anti-nucleocapsid IgG after the boost, consistent with unknown, asymptomatic SARS-CoV-2 infection during this period. Infection defined by anti-nucleocapsid IgG, whether known to participant or not, increased anti-spike IgG levels, relative to those lacking anti-nucleocapsid IgG, at 120 days post-booster.

No difference in anti-spike antibody and surrogate viral neutralization following SARS-CoV-2 booster vaccination in persons with HIV compared to controls (CO-HIV Study)

“…As an exploratory objective, we quantified anti-nucleocapsid IgG, using levels above 0.19 AU/mL as a proxy for prior infection ( 13 ). One interesting finding was that more PLWH had anti-nucleocapsid IgG levels that were indicative of prior infection, despite reporting similar rates of symptomatic SARS-CoV-2 infection as controls without HIV.…”

“…Ranges for anti-nucleocapsid IgG were 0.0170-70 AU/mL. For anti-nucleocapsid IgG response, we defined a cutoff of greater than 0.19 AU/mL, which is three standard deviations above the mean of pre-pandemic negative samples, as a proxy for prior SARS-CoV-2 infection ( 13 ). The Meso Scale Discovery antibody assay (Lot Number K0081945) conversion from MSD units (AU/mL) to WHO/NIBSC units (BAU/mL) can be calculated by multiplying MSD units by a conversion factor (0.00901 for anti-spike IgG and 0.00236 for anti-nucleocapsid IgG) ( 14 ).…”