Impact of maternal SARS-CoV-2 booster vaccination on blood and breastmilk antibodies.

Maternal COVID-19 vaccination could protect infants who are ineligible for vaccine through antibody transfer during pregnancy and lactation. We measured the quantity and durability of SARS-CoV-2 antibodies in human milk and infant blood before and after maternal booster vaccination. Prospective cohort of lactating women immunized with primary and booster COVID-19 vaccines during pregnancy or lactation and their infants. Milk and blood samples from October 2021 to April 2022 were included. Anti-nucleoprotein (NP) and anti-receptor binding domain (RBD) IgG and IgA in maternal milk and maternal and infant blood were measured and compared longitudinally after maternal booster vaccine. Forty-five lactating women and their infants provided samples. 58% of women were anti-NP negative and 42% were positive on their first blood sample prior to booster vaccine. Anti-RBD IgG and IgA in milk remained significantly increased through 120-170 days after booster vaccine and did not differ by maternal NP status. Anti-RBD IgG and IgA did not increase in infant blood after maternal booster. Of infants born to women vaccinated in pregnancy, 74% still had positive serum anti-RBD IgG measured on average 5 months after delivery. Infant to maternal IgG ratio was highest for infants exposed to maternal primary vaccine during the second trimester compared to third trimester (0.85 versus 0.29; p<0.001). Maternal COVID-19 primary and booster vaccine resulted in robust and long-lasting transplacental and milk antibodies. These antibodies may provide important protection against SARS-CoV-2 during the first six months of life.

Vaccination Beliefs and Attitudes of Lactating People During the SARS-CoV-2 Pandemic.

BACKGROUND: Pregnant and recently pregnant people have lower vaccination rates against SARS-CoV-2 than the general population, despite increased risk of adverse outcomes from infection. Little is known about vaccine hesitancy in this population. RESEARCH AIM: To characterize SARS-CoV-2 and other vaccine attitudes of lactating people who accepted the SARS-CoV-2 vaccine, describing their vaccine experiences to further contextualize their beliefs. METHODS: A prospective cross-sectional online survey design was used. We administered the survey to 100 lactating people in Pennsylvania from April to August 2021, upon enrollment into a longitudinal study investigating SARS-CoV-2 vaccine antibodies in human milk. This survey assessed SARS-CoV-2 vaccine attitudes, vaccine counseling from providers, and vaccine decision making. Associations between vaccination timing and beliefs were analyzed by Pearson chi-square. RESULTS: Of 100 respondents, all received ≥ 1 SARS-CoV-2 vaccine before or shortly after enrollment, with 44% (n = 44) vaccinated in pregnancy and 56% (n = 56) while lactating. Participants reported vaccination counseling by obstetric (n = 48; 70%) and pediatric (n = 25; 36%) providers. Thirty-two percent (n = 32) received no advice on SARS-CoV-2 vaccination from healthcare providers, while 69% (n = 69) were counseled that vaccination was safe and beneficial.While 6% (n = 6) and 5% (n = 5) reported concerns about the safety of maternal vaccines for lactating people or their infants, respectively, 12% (n = 12) and 9% (n = 9) expressed concerns about the safety of maternal SARS-CoV-2 vaccination in particular. CONCLUSIONS: Despite high uptake of SARS-CoV-2 vaccine among participants, safety concerns persisted, with many reporting a lack of direct counseling from providers. Future research should investigate how variability in provider counseling affects SARS-CoV-2 vaccine uptake in perinatal populations.