Persistence of Antibodies in Infants after Maternal COVID Vaccination or Natural Infection

A recent study evaluated the persistence of maternal anti-S IgG, induced by a COVID-19 vaccine, in infant blood, and compared the persistence of infant anti-S IgG following the mother’s vaccination with natural infection.

Women who had received an mRNA COVID-19 vaccine in pregnancy or were infected with COVID at 20 to 32 weeks’ gestation, had enrolled in a prospective study at 2 academic medical centers in Boston, and had enrolled their infants in this follow-up study, were included. Individuals infected before vaccination were excluded from the study. Investigators obtained matched maternal and umbilical cord serum samples at birth. Infant capillary serum samples were obtained 2 months following birth for infants of vaccinated mothers and after 6 months for infants of mothers who were vaccinated and mothers who had been infected with COVID-19. 

Antibody titers against the virus spike protein were assessed. The study included 77 vaccinated pregnant women and 12 with symptomatic COVID-19 infection in pregnancy. At 2 months, capillary serum samples were obtained from 49 infants of vaccinated mothers, and at 6 months, the samples were obtained from 28 infants of vaccinated mothers and 12 infants of infected mothers.

Findings from the study:

  • The titers were significantly higher among vaccinated mothers at delivery with a mean (SD) of 2.03 (0.47) optical density (OD450-570), in comparison with mothers after infection [mean (SD) of 0.65 (0.76) OD450-570] (P < .001). 
  • The mean (SD) cord titers were higher following vaccination compared to natural infection at 2.17 (0.50) OD450-570 and 1.00 (0.83) OD450-570, respectively (P < .001). 
  • At 2 months, 98% of infants of vaccinated mothers were found to have detectable anti-S IgG. 
  • The mean (SD) titer at 2 months was 1.29 (0.53) OD450-570, and correlated with both maternal and cord titers at delivery.
  • Vaccination was associated with significantly higher antibody persistence in infants compared to natural infection. 
  • At 6 months, 57% of infants of vaccinated mothers had detectable antibodies while only 8% of infants born to infected mothers had detectable levels (P = .005). 
  • The mean (SD) titer was 0.33 (0.46) OD450-570 among infants of vaccinated mothers and 0 (0.01) OD450-570 in infants of infected mothers (P = .004). Maternal (P = .23) or cord (P = .05) titers had no significant association with infant titers at 6 months.

It was shown that the majority of infants born to vaccinated mothers had persistence of anti-S antibodies at 6 months.

Source: Shook LL, Atyeo CG, Yonker LM, et al. Durability of Anti-Spike Antibodies in Infants After Maternal COVID-19 Vaccination or Natural Infection. JAMA. 2022 Feb 7.

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