What should I know about COVID-19 vaccines if I’m pregnant? Credit: Peter Hamlin / AP

Health officials recommend COVID-19 vaccines and boosters for people who are pregnant, breastfeeding and trying to become or planning on getting pregnant. The guidance is based on studies that show risks of severe disease are high among the group.

Now, a new study of more than 1,300 pregnant patients reveals how timing of coronavirus vaccination influences antibody levels at the time of delivery.

Researchers found antibodies at birth were highest among fully vaccinated pregnant patients without a history of COVID-19 who received their first Pfizer or Moderna shots during their third trimester. Antibody levels were lowest among those who were vaccinated before they got pregnant or during their first trimester, though researchers say the “difference wasn’t large.”

Generally, antibodies were detectable in the blood of parents and umbilical cords among all those who were fully vaccinated, regardless of vaccination timing, according to the study published Dec. 28 in the journal Obstetrics & Gynecology.

Only 20 patients in the study received a booster shot — all during their third trimester. On average, they had higher antibody levels in their blood than those with only two doses.

The Weill Cornell Medicine team found similar trends in umbilical cord blood antibody levels, offering more evidence of antibody transfer to babies in the womb. Studies show parental antibodies can travel through the placenta to the baby and via breast milk.

It’s important to note that protection against COVID-19 goes beyond antibodies. There are other components of the immune system that play important roles in warding off viruses and bacteria.

The takeaway, researchers say: Pregnant patients should not delay COVID-19 vaccination.

“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,” the study’s first author Dr. Yawei Jenny Yang, an assistant professor of pathology and laboratory medicine at Weill Cornell Medicine, said in a news release.

The study included 1,359 pregnant patients who gave birth at the NewYork-Presbyterian Alexandra Cohen Hospital for Women and Newborns after 34 or more weeks of pregnancy.

Among the 33 patients who received the Johnson & Johnson vaccine, data analysis showed “there was no significant difference” in antibody levels depending on vaccination timing. (The Centers for Disease Control and Prevention on Dec. 16 revealed its “clinical preference” for the Pfizer and Moderna vaccines over the J&J shot).

And among vaccinated patients who previously tested positive for COVID-19, antibody levels at the time of delivery were “moderately higher on average, and showed even less of a decline with earlier vaccination timing,” researchers said.

Pregnant patients who did not complete their vaccination series had “significantly lower” antibody levels at the time of birth compared to all other groups. What’s more, the team found their results were “consistent” with those of other vaccines pregnant patients receive, including the Tdap and flu shots, which protect the parent and baby.

CDC data shows the number of pregnant people who have contracted the coronavirus has increased in recent months, likely caused by the highly transmissible omicron variant. Most infections have occurred during patients’ third trimesters.

Health officials say the benefits of COVID-19 vaccines outweigh any known or potential risks.

On Sept. 29, the CDC issued an “urgent health advisory” stating the importance of COVID-19 vaccination among people who are pregnant, lactating, trying to become pregnant and planning on getting pregnant in the future following rises in hospitalizations.

A CDC study published in November 2020 found pregnant people who experience symptoms during their coronavirus infection face a two-fold risk of intensive care unit admission and a 70 percent increased risk of death. They are also more likely to have a preterm birth, stillbirth and a newborn infected with COVID-19 who requires ICU admission.

It’s unknown what risks the omicron variant provokes in pregnant people.

A study published in March 2021 found pregnant people gain similar levels of antibodies after vaccination compared with non-pregnant and non-lactating people.

Katie Camero, Washington McClatchy Bureau