Working at warp speed
Government scientists at the NIH were concerned about the risk of COVID-19 to pregnant people from the very beginning and knew that expectant moms needed vaccines as much or more than anyone else, said Larry Corey, MD, a leader of the COVID-19 Prevention Network, which coordinated COVID-19 vaccine trials for the federal government.
But including pregnant volunteers in the larger vaccine trials could have led to interruptions and delays, Dr. Corey said. Researchers would have had to enroll thousands of pregnant volunteers to achieve statistically robust results that weren’t due to chance, he said.
Pregnancy can bring on a wide range of complications: gestational diabetes, hypertension, anemia, bleeding, blood clots, or problems with the placenta, for example. Up to 20% of people who know they’re pregnant miscarry. Because researchers would have been obliged to investigate any medical problem to make sure it wasn’t caused by one of the COVID-19 vaccines, including pregnant people might have meant having to hit pause on those trials, Dr. Corey said.
With death tolls from the pandemic mounting, “we had a mission to do this as quickly and as thoroughly as possible,” Dr. Corey said. Making COVID-19 vaccines available within a year “saved hundreds of thousands of lives.”
The first data on COVID-19 vaccine safety in pregnancy was published in April of 2021 when the CDC released an analysis of nearly 36,000 vaccinated pregnant people who had enrolled in a registry called V-safe, which allows users to log the dates of their vaccinations and any subsequent symptoms.
Later research showed that COVID-19 vaccines weren’t associated with increased risk of miscarriage or premature delivery.
Brenna Hughes, MD, a maternal-fetal medicine specialist and member of the American College of Obstetricians and Gynecologists’ COVID-19 expert group, agrees that adding pregnant people to large-scale COVID-19 vaccine and drug trials may have been impractical. But researchers could have launched parallel trials of pregnant women, once early studies showed the vaccines were safe in humans, she said.
“Would it have been hard? Everything with COVID is hard,” Dr. Hughes said. “But it would have been feasible.”
The FDA requires that researchers perform additional animal studies – called developmental and reproductive toxicity studies – before testing vaccines in pregnant people. Although these studies are essential, they take 5-6 months, and weren’t completed until late 2020, around the time the first COVID-19 vaccines were authorized for adults, said Emily Erbelding, MD, director of microbiology and infectious diseases at the National Institute of Allergy and Infectious Diseases, part of the NIH.
Pregnancy studies “were an afterthought,” said Irina Burd, MD, director of Johns Hopkins’ Integrated Research Center for Fetal Medicine and a professor of gynecology and obstetrics. “They should have been done sooner.”
The NIH is conducting a study of pregnant and postpartum people who decided on their own to be vaccinated, Dr. Erbelding said. The study is due to be completed by July 2023.
Janssen and Moderna are also conducting studies in pregnant people, both due to be completed in 2024.
Pfizer scientists encountered problems when they initiated a clinical trial, which would have randomly assigned pregnant people to receive either a vaccine or placebo. Once vaccines were widely available, many patients weren’t willing to take a chance on being unvaccinated until after delivery.
Pfizer has stopped recruiting patients and has not said whether it will publicly report any data from the trial.
Dr. Hughes said vaccine developers need to include pregnant people from the very beginning.
“There is this notion of protecting pregnant people from research,” Dr. Hughes said. “But we should be protecting patients through research, not from research.”