Neutralizing Antibodies Against the SARS-CoV-2 Omicron Variant (BA.1) 1 to 18 Weeks After the Second and Third Doses of the BNT162b2 mRNA Vaccine

Abstract

This cohort study examines neutralizing antibodies against the SARS-CoV-2 Omicron variant (BA.1) after the second and third doses of the BNT162b2 mRNA vaccine among Danish adults.

Figure 1.. Temporal Virus Neutralizing Antibody Responses Against Ancestral SARS-CoV-2 Strain (D614G), Delta Variant (B.1.617.2), and Omicron Variant (B.1.1.529, BA.1)

A, Live virus neutralization titers for a cross-sectional cohort of individuals vaccinated with BNT162b2 (Pfizer/BioNTech) vaccine (n = 128) at 4 to 18 weeks following the second dose in the primary 2-dose vaccination series and 1 to 8 weeks following a third BNT162b2 dose administered more than 4 months after the second dose. B, Live virus neutralization titers stratified by age group 4 to 18 weeks after the primary 2-dose BNT162b2 vaccination series and 1 to 8 weeks after the third BNT162b2 dose. C, In a longitudinal cohort of individuals (n = 7) who became infected before January 2021—before the Alpha and Delta variants became dominant in Denmark—virus neutralization titers were determined 46 to 186 days after a polymerase chain reaction positive test (median: 65 days) and after subsequent vaccination more than 6 months after the infection, primarily within 5 weeks postvaccination. The viral targets in the microneutralization assays were Danish clinical isolates passaged twice in Vero E6 cells and sequenced to confirm lineage-specific spike variations. Data points represent individual 50% serum neutralization titers. Bars represent the geometric mean titer (indicated above bar) and error bars the 95% CI. The lower limit of quantitation (LLOQ) was 10 and all values below the LLOQ were set to 0.5 times the LLOQ.

Figure 2.. Temporal Omicron Virus Neutralization Titers Following 2 or 3 BNT162b2 Doses in Different Age Groups

Individuals who received the primary 2-dose BNT162b2 vaccination series (n = 73; sampling between peak responses at 4 weeks and the last time point, 16 weeks, after dose 2) or 3 BNT162b2 doses (n = 35; sampling between peak responses at 3 weeks and the last time point, 8 weeks) were categorized according to 2 different age groups: less than or equal to 65 years of age and greater than 65 years of age. Omicron-specific neutralization titers for each age group were stratified according to time after vaccine dose. The dot plots represent 50% serum neutralization titers relative to day of sample collection after the second or third BNT162b2 dose for each age group. Each data point presents an individual sample; the black lines represent the linear regression curve and the shaded areas the 95% CI. The association between the 2 continuous variables were assessed using the Spearman correlation test.