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Maternal COVID-19 Vaccination and Prevention of Symptomatic Infection in Infants
Cristina V Cardemil1, Yi Cao2, Christine M Posavad2
1National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland.
Insights
Maternal COVID-19 vaccination boosts infant antibody levels, significantly reducing infection risk in the first six months. A booster dose further amplifies this passive protection against SARS-CoV-2.
Area of Science:
- Immunology
- Maternal and Child Health
- Infectious Diseases
Background:
- Maternal vaccination during pregnancy is a strategy to protect infants from infectious diseases.
- Infant protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is crucial in early life.
Purpose of the Study:
- To quantify the protective effect of maternally derived vaccine-induced antibodies against infant coronavirus disease 2019 (COVID-19) infection.
- To assess protection in the first six months of life.
Main Methods:
- Infants born to mothers vaccinated with mRNA COVID-19 vaccines (2 or 3 doses) had antibody titers measured at delivery.
- Infant SARS-CoV-2 infection was tracked through prospective follow-up to 6 months.
- Risk reduction was estimated based on maternal vaccination dose and infant antibody titer levels.
Main Results:
- Infants of boosted mothers had higher antibody titers and were 56% less likely to be infected.
- Each 10-fold increase in antibody titers (Spike IgG, pseudovirus, live virus) at delivery correlated with significant risk reduction (30%-60%) for infant infection.
- Protection was observed against various SARS-CoV-2 strains, including Omicron variants.
Conclusions:
- Higher transplacental antibody titers substantially reduce infant SARS-CoV-2 infection risk.
- Maternal vaccination, especially with a booster dose, amplifies protection during periods of viral predominance.
- Maternal vaccination offers crucial passive immunity to infants before they are eligible for vaccination.
Background And Objectives:
Maternal vaccination may prevent infant coronavirus disease 2019 (COVID-19). We aimed to quantify protection against infection from maternally derived vaccine-induced antibodies in the first 6 months of an infant's life.
Methods:
Infants born to mothers vaccinated during pregnancy with 2 or 3 doses of a messenger RNA COVID-19 vaccine (nonboosted or boosted, respectively) had full-length spike (Spike) immunoglobulin G (IgG), pseudovirus 614D, and live virus D614G, and omicron BA.1 and BA.5 neutralizing antibody (nAb) titers measured at delivery. Infant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection was determined by verified maternal-report and laboratory confirmation through prospective follow-up to 6 months of age between December 2021 and July 2022. The risk reduction for infection by dose group and antibody titer level was estimated in separate models.
Results:
Infants of boosted mothers (n = 204) had significantly higher Spike IgG, pseudovirus, and live nAb titers at delivery than infants of nonboosted mothers (n = 271), and were 56% less likely to acquire infection in the first 6 months (P = .03). Irrespective of boost, for each 10-fold increase in Spike IgG titer at delivery, the infant's risk of acquiring infection was reduced by 47% (95% confidence interval 8%-70%; P = .02). Similarly, a 10-fold increase in pseudovirus titers against Wuhan Spike, and live virus nAb titers against D614G, and omicron BA.1 and BA.5 at delivery were associated with a 30%, 46%, 56%, and 60% risk reduction, respectively.
Conclusions:
Higher transplacental binding and nAb titers substantially reduced the risk of SARS-CoV-2 infection in infants, and a booster dose amplified protection during a period of omicron predominance. Until infants are age-eligible for vaccination, maternal vaccination provides passive protection against symptomatic infection during early infancy.
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