COVID-19 vaccination during pregnancy protects babies from SARS-CoV-2 infection in their first 4 months of life, according to a study yesterday in JAMA Internal Medicine.In the cohort study, which included all infants born in Norway late last year and early this year, COVID-19 incidence was lower in babies born to women who received either the Moderna or Pfizer-BioNTech vaccine during the second or third trimester of pregnancy.Protection, however, was more than twice as high during the period dominated by the Delta variant as during the Omicron period.Protection for infants 33% during OmicronThe researchers—primarily from the Norwegian Institute of Public Health—note that studies have shown that babies born to women vaccinated during pregnancy are protected against diseases like pertussis (whooping cough) and flu.
So they aimed to assess whether the phenomenon held true for COVID vaccines.They note that, of 21,643 Norwegian babies born from September 2021 through February 2022, 9,739 of them (45.0%) were born to women who received a second or third dose of an mRNA COVID-19 vaccine during pregnancy.The investigators analyzed data on polymerase chain reaction (PCR) test results for mothers and their babies, all of which are registered in the Norwegian Surveillance System for Communicable Diseases.
They included data on the first SARS-CoV-2–positive PCR test for babies at least 1 day after birth up to 4 months of age, as well as information on women who had a positive test 14 or more days before giving birth.
In Norway, free PCR tests are widely available.The incidence rate of a positive COVID-19 test for infants 0 to 4 months old overall was 5.8 per 10,000 follow-up days.