A booster dose of either BNT162b2 or mRNA-1273 mRNA vaccines induces a
robust recall of anti-SARS-CoV-2 spike protein IgG antibodies in saliva
Abstract
Saliva specimens offer practical advantages over serum specimens for
studying SARS-CoV-2 immunity following natural infections or
vaccination. Salivary anti-spike (S)-protein immunoglobulin G (IgG)
antibody titers are quantifiable by ELISA with high sensitivity and
specificity and robustly correlated with serum titers. Our longitudinal
prospective study enrolled participants who received two-dose regimen
vaccination with either mRNA-1273 or BNT162b2 vaccines, and salivary
anti-S-protein IgG titers were measured at intervals for its duration.
Subsequently, participants received homologous mRNA-1273 (n=28) and
BNT162b2 (n=29) booster vaccines and enrolled in the booster study.
Participants performed self-collection of saliva specimens with the
OraSure ® device at predetermined time intervals for
each cohort. Salivary anti-S-protein IgG titers varied between
participants following the second dose; titers waned from their peak 9
to 150-fold in the mRNA-1273 cohort and 7 to 105-fold in the BNT162b2
cohort. The booster dose elicited a 2 to 238-fold increase in the
mRNA-1273 cohort and a 20 to 255-fold increase in the BNT162b2 cohort
from the lowest titer. These results replicate the antibody waning and
recall trends following second and third doses reported in larger
studies using serum specimens, supporting the use of non-invasive saliva
specimens to monitor antibody titers during future epidemics or
vaccination campaigns.