Anytime Is the Right Time for COVID Vaccine in Pregnancy

The best time during pregnancy to get a COVID-19 vaccine appears to be right now.

A new study found that antibodies to the SARS-CoV-2 virus in nearly 1,400 women and their babies at the time of delivery didn’t vary dramatically based on when a woman got her vaccine during pregnancy.

“Women often ask what is the best vaccination timing for the baby — our data suggest that it’s now,” study co-author Dr. Malavika Prabhu said in a news release from Weill Cornell Medicine. She is an assistant professor and ob-gyn at New York-Presbyterian/Weill Cornell Medical Center in New York City.

For the study, researchers at the two institutions measured antibody levels in the mothers’ blood and the babies’ umbilical cord blood.

While levels were higher when vaccination occurred in a woman’s third trimester, they were comparably high and likely protective when vaccination happened early in pregnancy or even a few weeks before, the study found.

A booster shot late in pregnancy can also make those antibody levels much higher, researchers said.

They said expectant mothers should not delay COVID-19 vaccination until late pregnancy.

“The message here is that you can get vaccinated at any point during pregnancy and it is likely going to be beneficial to you and your baby at the time of birth — and of course by getting vaccinated early you will be protecting yourself and your baby throughout the pregnancy,” said first author Dr. Yawei Jenny Yang, an assistant professor of pathology and laboratory medicine at Weill Cornell.

The researchers analyzed antibodies in 1,359 pregnant women who had been vaccinated for COVID-19 during or up to six weeks before pregnancy and who gave birth after at least 34 weeks’ gestation.

Antibodies were generally detectable at delivery in both maternal and cord blood among all the fully vaccinated women.

Among women with no history of SARS-CoV-2 infection who received the two-dose Pfizer or Moderna mRNA vaccine, antibody levels at delivery were lowest among those who were vaccinated before pregnancy or in their first trimester. Levels were highest after third trimester vaccination, but the difference wasn’t large.

There was no significant difference in antibody levels by timing of vaccination in women who received the Johnson & Johnson single-dose vaccine, though few in the study had received that shot.

Among vaccinated women who had a prior history of COVID-19 infection, antibody levels at delivery in maternal and cord blood were moderately higher on average. They also showed even less of a decline with earlier vaccination timing.

On average, the 20 women who reported having a booster dose in their third trimester had higher levels of antibodies.

Women who had not finished their vaccine series by the time they delivered had significantly lower antibody levels than all other groups — as did the offspring’s cord blood.

“These study results are consistent with what we see with other maternal vaccines such as flu and Tdap, which, when given during pregnancy, protect the mother and baby,” said senior author Dr. Laura Riley, obstetrician and gynecologist-in-chief at New York-Presbyterian/Weill Cornell Medical Center.

The U.S. Centers for Disease Control and Prevention recommends COVID-19 vaccination for pregnant women.

Studies of the commonly used vaccines so far have found no increased rate of adverse side effects for mothers or their babies, while research has suggested that COVID-19 illness tends to be more severe for women when they are pregnant. Past studies have also suggested the virus increases the risks of preterm birth, stillbirth and other adverse outcomes.

The findings were published Dec. 28 in the journal Obstetrics & Gynecology. The researchers plan to examine vaccine and booster effects in the context of the new Omicron variant.

More information

The U.S. Centers for Disease Control and Prevention has more information on COVID-19 and pregnancy.

SOURCE: Weill Cornell Medicine, news release, Dec. 28, 2021