Maternal vaccination reduces newborn COVID-19 hospitalization risk by 61%

Robyn Horsager-Boehrer, M.D.
Obstetrics and Gynecology

six-month study published by the Centers for Disease Control and Prevention (CDC) found that maternal vaccination for COVID-19 reduced newborns’ risk of hospitalization due to the virus by approximately 61%.

The benefit jumps to 80% if the two vaccine doses are given after 21 weeks of pregnancy and more than two weeks before delivery. Antibodies made after a pregnant woman is vaccinated will cross the placenta and enter the fetal blood stream, protecting the newborn.

These outcomes are 11-30% better than goals set at the start of the pandemic. Before the vaccines were developed, the World Health Organization had hoped for at least 50% risk reduction in adults and children.

If you are pregnant and want to be vaccinated, you should not wait until the 21-week mark of pregnancy to get your jab. Getting vaccinated at any time in pregnancy protects your health, which reduces COVID-19 related risks to your pregnancy, such as:

• Increased rates of preterm birth and stillbirth
• Severe illness requiring hospitalization
• Needing to be placed on a ventilator to breathe
• Maternal death
• In utero COVID-19 infection

The new CDC study supports previous findings that the COVID-19 vaccines are safe and effective for in pregnancy – and that your newborn can benefit from your vaccination for at least six months after birth.

Dramatic benefits for newborns

The study, performed from July 1, 2021, through January 17, 2022, included 379 babies who were admitted at 20 pediatric hospitals across the U.S. These babies were in utero during the Delta and/or Omicron waves.

One hundred seventy-six of the infants were hospitalized due to their COVID-19 infections – 25% of those were admitted to the intensive care unit (ICU) and 15% were critically ill, requiring life support. The majority of babies admitted to the ICU (88%) were born to women who were not vaccinated during pregnancy. Tragically, one infant died from COVID-19 infection.

For the study, women were not considered fully vaccinated during pregnancy if they had:

• Only one dose of an mRNA vaccine (Pfizer or Moderna)
• The one-dose Johnson & Johnson vaccine
• Been vaccinated prior to becoming pregnant or after delivery

Researchers asked the babies’ birth mothers about their COVID-19 vaccine history: type of vaccine, number of doses received, and the dates they received the doses. Based on the babies’ birthdates, the researchers could determine the gestational timeline of when the doses were given. This is important because if a shot was given within two weeks before delivery, there is not optimal time for maternal antibody production and transfer to the fetus.

Babies whose birth mothers had been fully vaccinated overall were 61% less likely to be hospitalized with a COVID-19 infection. Babies were 80% less likely to be hospitalized with the virus if their birth mothers had two doses of the vaccine between 21 weeks of pregnancy and more than two weeks before delivery.

Prenatal vaccines have a proven history

Prenatal vaccination is proven to prevent several types of serious infections in newborns. Prior to COVID-19, pertussis (whooping cough) was the most recent risk-reduction opportunity.

The maternal Tdap vaccine – tetanus, diphtheria, and pertussis – is proven safe and, when given during pregnancy, highly effective against newborn whooping cough. Babies cannot be vaccinated themselves for whooping cough until they are 2 months old.

Whooping cough vaccines have been strongly advised in pregnancy for several years. However, many providers and patients thought that one vaccination would cover a patient’s current and future pregnancies.

In 2013, the Advisory Committee on Immunization Practices (ACIP) updated its guidelines to recommend prenatal vaccination in the third trimester for each individual pregnancy due to rising numbers of cases of pertussis in the United States.

Before the change, 75% of babies in the U.S. who got whooping cough had to be admitted to the hospital and 1 in 100 died. Since the guidelines were updated, studies have shown the Tdap vaccine to be 78% effective in preventing pertussis and 90% in preventing hospitalization in infants under 2 months old.

The COVID-19 maternal prenatal vaccination strategy mirrors that for Tdap vaccine: Women who choose to be vaccinated during pregnancy should do so before the two weeks prior to delivery, providing enough time to produce antibodies that can cross the placenta and reach the baby before birth.