Study: Prenatal vaccination protects infants from COVID-19
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Key takeaways:
- Infants were protected from COVID-19 if their mothers received a vaccine during pregnancy.
- Vaccine efficacy increased to over 44% if mothers received a booster dose.
Prenatal vaccination protects infants from COVID-19 up to age 6 months, real-world study findings published in JAMA Network Open suggest. The study found that vaccination prior to pregnancy did not protect babies from the disease.
“There are limited real-world data on the effectiveness of maternal vaccination in protecting infants from COVID-19 infection, especially in Asia,” Orlanda Goh, MBBS, MPH, associate consultant in the department of internal medicine at Singapore General Hospital, told Healio. “There are also no data comparing vaccine effectiveness before and during pregnancy.”
Goh said previous studies have “simply compared between pregnant women who were unvaccinated vs. vaccinated.”
“This is highly relevant in the current context, where many pregnant women have been vaccinated before their pregnancy,” Goh said. “We found it important to generate this evidence so doctors can provide recommendations and pregnant mothers can make informed decisions on getting vaccinated during pregnancy.
Goh and colleagues also aimed to determine whether being vaccinated during pregnancy vs. before pregnancy reduced the risks for infants.
For the study, the researchers reviewed the records of all infants born to Singaporeans and permanent residents between Jan. 1, 2022, and Sept. 30, 2022.
“To reduce bias, we only selected infants who were definitely exposed to the virus through their parent or parents being infected after they were born,” Goh said. “Maternal vaccination status and sociodemographic details — as well parental and infant infection statuses — were extracted from our national database.”
The authors compared the risk for infant infection among those whose mothers were unvaccinated, vaccinated before pregnancy or vaccinated during pregnancy.
“We found that maternal vaccination was associated with a lower risk of COVID-19 infection among infants up to 6 months of age during the omicron waves,” Goh said. “However, this effect was only seen if the vaccine was given during pregnancy.”
Among the 7,292 infants included in the analysis, 97.6% were born to mothers who were fully vaccinated or boosted as of 14 days before delivery with messenger RNA vaccines. Of this subgroup, 39.5% were born to mothers who received their second dose during pregnancy, and 50.2% were born to mothers who received a third dose, or booster, during pregnancy.
The researchers found that vaccine efficacy was 15.4% (95% CI, –17.6% to 39.1%) for infants born to any mothers vaccinated before pregnancy and increased to 41.5% (95% CI, 22.8% to 55.7%) for infants born to mothers who were vaccinated during pregnancy. Vaccine efficacy increased to 44.4% if a mother received a third dose.
The results were novel in that they confirmed in a real-world setting that vaccination before pregnancy did not protect newborn babies from getting COVID-19, Goh said.
“We showed that there was infant protection against the omicron XBB variant for those born to mothers who received their vaccination during pregnancy,” Goh said.
“Pregnant women cannot depend on COVID-19 vaccines they received prior to getting pregnant for protection of their newborn baby against COVID-19,” Yung Chee Fu, MBChB, senior consultant in the infectious disease service at the department of pediatrics at KK Women’s and Children’s Hospital in Singapore and co-author of the study, told Healio. “[Further studies should] continue monitoring of real-world vaccine effectiveness of maternal COVID-19 vaccination from updated vaccines and against newly emergent SARS-CoV-2 variant.”
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