Summary
Most babies born to COVID-19 vaccinated mothers have persistent anti-spike (anti-S) antibodies at six months, according to a research letter published in the Journal of the American Medical Association .
Lydia L. Shook, MD, of Massachusetts General Hospital in Boston, and colleagues characterized the persistence of vaccine-induced maternal anti-S immunoglobulin G (IgG) in the infant’s blood after maternal vaccination versus natural infection . People who received a COVID-19 mRNA vaccine during pregnancy or who were infected with severe acute respiratory syndrome coronavirus 2 between 20 and 32 weeks of gestation were enrolled (77 and 12 mothers, respectively).
The researchers found that at delivery, vaccinated mothers had significantly higher titers, with a mean optical density of 2.03 compared to an optical density of 0.65 (OD450 to 570) for mothers after infection. . Mean cord titers were also higher after vaccination versus natural infection (2.17 versus 1.00 OD450 to 570).
Ninety-eight percent of babies of vaccinated mothers had detectable anti-S IgG at two months. The mean titer at two months was 1.29 OD450 to 570 and correlated with maternal and cord titers at delivery.
At six months, 57 percent versus 8 percent of babies born to vaccinated versus infected mothers had detectable antibodies, with mean titers of 0.33 and 0 OD450 to 570, respectively. No correlation was observed between maternal or umbilical cord titers with infant anti-S titers at six months.
"Pregnant women are at extremely high risk for serious complications from COVID," a co-author said in a statement. "And given the delay in the development of COVID-19 vaccines for babies, these data should motivate mothers to get vaccinated and even get a booster shot during pregnancy to boost their babies’ defenses against COVID."
COVID-19 vaccination during pregnancy generates functional anti-spike (anti-S) IgG antibodies in the maternal circulation that are detectable in umbilical cord blood at birth and may protect the newborn and infant from COVID-19. 19. Umbilical cord Anti-S IgG titers correlate with maternal titers and are highest after vaccination in the late second and early third trimesters.
We characterized the persistence of vaccine-induced maternal anti-S IgG in infant blood and compared the persistence of infant anti-S IgG after maternal vaccination versus natural infection.
Methods
The study included people who had received a COVID-19 mRNA vaccine during pregnancy or who were infected with SARS-CoV-2 between 20 and 32 weeks of gestation, were enrolled in a prospective study at 2 centers academic doctors in Boston and had enrolled their babies in this follow-up study conducted from July 21, 2021 to October 22, 2021.
Individuals vaccinated or infected between 20 and 32 weeks’ gestation were enrolled because previous studies demonstrated superior transplacental transfer of antibodies during this window compared with vaccination closer to delivery. 4, 5Those infected before vaccination were excluded.
Maternal serum and umbilical cord samples were collected at birth. Infant capillary serum samples were collected using a microneedle device at 2 months after birth for infants of vaccinated mothers and at 6 months for infants of vaccinated mothers and SARS-CoV-2-infected mothers.
Antibody titers against the SARS-CoV-2 spike protein were quantified using an enzyme-linked immunosorbent assay. Differences in titers between the vaccinated and infected groups at delivery and at 6 months of age were evaluated by the Mann-Whitney test.
Differences in the proportions of infants with detectable antibodies at 6 months were assessed using Fisher’s exact test. The correlation between calving titers and infant antibodies was assessed using Spearman’s rank test. Analyzes were performed using Prism version 9.0. Significance was defined as a 2-sided p < 0.05. The study was approved by the Mass General Brigham institutional review board and all participants provided written informed consent.
Results
77 vaccinated pregnant mothers and 12 with symptomatic SARS-CoV-2 infection during pregnancy were included . At 2 months, hair serum samples were collected from 49 infants of vaccinated mothers; At 6 months, serum samples were collected from 28 infants of vaccinated mothers (mean, 170 days after birth) and 12 infants of infected mothers (mean, 207 days after birth).
Vaccinated mothers had significantly higher titers at delivery with a mean (SD) of 2.03 (0.47) optical density (OD 450-570) compared to mothers after infection with a mean (SD) of 0.65 (0.76) OD 450-570 (P < .001).
Similarly, the respective mean (SD) cord titers were higher after vaccination versus natural infection: 2.17 (0.50) OD 450-570 vs 1.00 (0.83) OD 450 -570 (p < 0.001).
Among infants of mothers vaccinated at 2 months, 98% (48 of 49) had detectable anti-S IgG. The mean (SD) titer at 2 months was 1.29 (0.53) OD 450-570, which was correlated with both maternal values (r = 0.55, P < 0.001) and cord titers (r = 0.43, P = 0.01) at delivery.
Vaccination resulted in significantly greater antibody persistence in infants than infection. At 6 months, 57% (16 of 28) of infants born to vaccinated mothers had detectable antibodies compared with 8% (1 of 12) of infants born to infected mothers ( P = 0.005).
Titers were a mean (SD) of 0.33 (0.46) OD 450-570 among infants of vaccinated mothers and 0 (0.01) OD 450-570 among infants of infected mothers (P = 0.004, Figure ). Neither maternal (p = 0.23) nor umbilical cord (p = 0.05) titers were significantly correlated with infants’ anti-S titers at 6 months, largely because 43% of infants they had no detectable titers at that time.
Discussion
This study found that most babies born to COVID-vaccinated mothers had persistent anti-S antibodies at 6 months, compared to babies born to mothers with SARS-CoV-2 infection.
Understanding the persistence of maternal antibody levels in infants is important because COVID-19 infections in this age group represent a disproportionate burden of pediatric morbidity associated with SARS-CoV-2 and because COVID-19 vaccines are currently not They are planned to be given to babies younger than 6 months.
Limitations of the study include the small number of infants, the longer average time to follow-up in the infected group (due to pragmatic limitations related to the timing of COVID-19 surges in Boston, and the availability of participants for follow-up. timely) and reporting antibody titers rather than clinical results.
Although the titer of antibodies known to protect against COVID-19 in infants is unknown, these findings provide additional incentive for pregnant people to seek the COVID-19 vaccine.
