Comparison of total and neutralizing SARS-CoV-2 spike antibodies against omicron and other variants in paired samples after two or three doses of mRNA vaccine.

Recognizing that anti-SARS-CoV-2 antibody levels wane over time following the 2-dose SARS-CoV-2 mRNA series, the FDA approved a booster dose for people greater than 12 years old. Limited data exist on whether a booster dose of the mRNA vaccine results in greater antibody protection than the primary series. We examined total and neutralizing antibodies to the spike protein of SARS-CoV-2, and neutralizing antibodies against Washington-1 (WA-1) and variants of concern (VOC) including Beta, Delta and Omicron in a longitudinal cohort. Healthcare workers (HWs) were included in the analysis if serum was collected 1) within 14-44 days post-dose2 of an mRNA SARS-CoV-2 vaccine (Timepoint 1, TP1), or 2) at least 8 months post-dose2 (Timepoint 2, TP2), or 3) within 14-44 days following mRNA booster (Timepoint 3, TP3). HWs with prior covid-positive PCR were excluded. We found that there is little to no neutralizing capability following a 2-dose mRNA vaccine series against the omicron variant, and neutralizing capacity to any variant strain tested has been lost by 8-months post two-dose vaccination series. However, the mRNA booster series eliminates the immune escape observed by the omicron variant with the two-dose series. Neutralizing titers were significantly higher for all variants post-boost compared to the titers post two-dose series. The longitudinal nature of our cohort facilitated the analysis of paired samples pre and post boost, showing a greater than 15-fold increase in neutralization against omicron post-boost in these paired samples. An mRNA booster dose provides greater quantity and quality of antibodies compared to a two-dose regimen and is critical to provide any protection against the omicron variant.