Infants remain at high risk for severe coronavirus disease 2019 (COVID-19).Human milk contains high levels of protective SARS CoV-2 specific antibodies post-infection and primary vaccine series, but levels decline over time.We hypothesized that the COVID-19 booster vaccine augment antibody production and the protection afforded to human milk-fed infants.We prospectively enrolled pregnant or lactating mothers planning to receive COVID-19 vaccination.
We measured human Pycnogenol milk IgG, IgA, and IgM antibodies targeting the SARS CoV-2 receptor binding domain within the spike protein and human milk neutralization activity against SARS CoV-2 in 10 lactating mothers from pre-COVID-19 primary series vaccine to post-booster dose.Human milk SARS CoV-2 specific IgG increased significantly from pre- to post-booster levels (median OD 0.33 vs.2.
02, P = 0.002).The IgG levels post-booster were even higher than the peak level after the primary series (2.02 vs.
0.95, P = 0.03).The increase in SARS CoV-2 specific IgA levels was not significant (0.
10 vs.0.33, P = 0.23).
There was a strong correlation between paired maternal blood and milk IgG and IgA levels (IgG rho 0.52, P < 0.001, IgA rho 0.31, P = 0.
05).Post-booster neutralizing activity was elevated compared to pre-booster levels (66% vs.12% inhibition, P = 0.002).
COVID-19 vaccine booster elicits SARS CoV-2 FPV Gear specific antibodies in human milk at higher levels compared to the initial primary series.This finding suggests that three doses of COVID-19 mRNA vaccination leads to improved mucosal response in human milk and reinforces current guidance recommending all pregnant or lactating mothers receive full COVID-19 vaccine courses with a booster dose.