In an early analysis of the coronavirus vaccine’s safety data, researchers at the Centers for Disease Control and Prevention found no evidence that the Pfizer-BioNTech or Moderna vaccines pose serious risks in pregnancy.
The findings are preliminary and only pertain to the first 11 weeks of the US vaccination program. But the study, which included self-reported data from more than 35,000 people who received one of the vaccines during or shortly before pregnancy, is the largest to date on the safety of the coronavirus vaccines in pregnant people.
Pregnant women were excluded from the clinical studies with the vaccines. This left patients, doctors and experts unsure whether the injections were safe to administer during pregnancy.
“There is a lot of concern about whether it is safe and whether it would work and what to expect in terms of side effects,” said Dr. Stephanie Gaw, a specialist in maternal-fetal medicine at the University of California, San Francisco.
The new data, said Dr. Gaw, show that “many pregnant people receive the vaccine, there is currently no significant increase in adverse pregnancy effects, and that side effect profiles are very similar to non-pregnant people.”
“I think that’s all very reassuring,” she said, “and I think it will really help healthcare providers and public health officials get the vaccine during pregnancy.”
Covid-19 carries serious risks during pregnancy. Pregnant women who develop symptoms of the disease are more likely to become seriously ill and die than non-pregnant women with symptoms.
Because of those risks, the CDC has recommended making coronavirus vaccines available to pregnant women, but it also suggests that they consult their doctor when making a vaccination decision.
The new study, published Wednesday in The New England Journal of Medicine, is based largely on self-reported data from V-safe, the CDC’s coronavirus vaccine safety control system. Program participants use a smartphone app to take regular surveys about their health and any side effects they experience after receiving a Covid-19 vaccine.
The researchers analyzed the side effects reported by V-safe participants who received the Pfizer or Moderna vaccine between December 14, 2020 and February 28, 2021. They focused on 35,691 participants who said they were pregnant when they received or received the vaccine pregnant shortly afterwards.
After vaccination, pregnant participants reported the same general pattern of side effects as non-pregnant, the researchers found: injection site pain, fatigue, headache, and muscle aches.
What you need to know about the Johnson & Johnson vaccine break in the US
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- On April 13, 2021, US health authorities called for an immediate discontinuation of Johnson & Johnson’s single-dose Covid-19 vaccine after six recipients in the United States developed a rare blood clot condition within one to three weeks of vaccination.
- All 50 states, Washington, DC and Puerto Rico has temporarily discontinued use of the vaccine or recommended providers. The U.S. military, federally-run vaccination sites, and a host of private companies, including CVS, Walgreens, Rite Aid, Walmart, and Publix, also stopped the injections.
- Less than one in a million vaccinations for Johnson & Johnson is now being investigated. If there is indeed a risk of blood clots from the vaccine – which has yet to be determined – that risk is extremely low. The risk of getting Covid-19 in the United States is much higher.
- The pause could complicate the nation’s vaccination efforts at a time when many states are facing an increase in new cases and the reluctance to tackle vaccinations.
- Johnson & Johnson had also decided to delay the rollout of its vaccine in Europe due to concerns about rare blood clots, but later decided to resume its campaign after the European Union’s drug regulator said a warning label should be added. South Africa, devastated by a more contagious variant of the virus emerging there, suspended use of the vaccine and Australia announced it would not purchase doses.
Women who were pregnant were slightly more likely to report injection site pain than women who were not, but less likely to report the other side effects. They also reported slightly more nausea or vomiting after the second dose.
Pregnant V-safe participants were also given the opportunity to enroll in a special registry that tracks pregnancy and infant outcomes.
By the end of February, 827 of those enrolled in the pregnancy registry had completed their pregnancies, 86 percent of which resulted in a live birth. The rates of miscarriage, preterm birth, low birth weight and birth defects were consistent with those reported in pregnant women before the pandemic, the researchers report.
“This study is critical for pregnant individuals,” said Dr. Michal Elovitz, a specialist in maternal and fetal medicine at the University of Pennsylvania, in an email. “It is very reassuring that no acute events have been reported in pregnant individuals” in the course of the study, she said.
But the report has several limitations and much more research is needed, experts said. Enrollment in the surveillance programs is voluntary and the data is self-reported.
In addition, because the study period included only the first months of the US vaccination campaign, the vast majority of those enrolled in the pregnancy registry were health professionals. And there is still no data on pregnancy outcomes of people vaccinated during the first trimester of pregnancy.
“I think we can have more confidence in recommending the vaccine during pregnancy, and especially in pregnant people at risk for Covid,” said Dr. Go away. ‘But we’ll do it should wait for more data for full pregnancy outcomes from vaccines in early pregnancy. “