Large U.S. COVID-19 vaccine trials will exclude pregnant women for now

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The first two COVID-19 vaccines to enter large-scale U.S. trials will not be tested in pregnant women this year, raising questions about how this vulnerable population will be protected from the coronavirus, researchers told Reuters.

Moderna and Pfizer, which has partnered with Germany’s BioNTech, this week separately launched clinical trials that use a new and unproven gene-based technology. Both companies are requiring proof of a negative pregnancy test and a commitment to using birth control from women of childbearing age who enroll.

Drugmakers say they first need to make sure the vaccines are safe and effective more generally. In addition, U.S. regulators require that drugmakers conduct safety studies in pregnant animals before the vaccines are tested in pregnant women to ensure they don’t harm the fetus or lead to miscarriage.

Bioethicists, vaccine and maternal health experts have argued for years that pregnant women should be included early in trials of pandemic vaccines so they would not need to wait until long after a successful candidate emerges. That debate fell on deaf ears in recent outbreaks of Ebola and Zika, but has taken on new urgency in the era of COVID-19, as studies show pregnant women are at increased risk of severe disease from the new coronavirus.

“It’s a problem because if (vaccines) are not tested in pregnancy, then they may not be available or people may not be comfortable offering them,” said Dr. Denise Jamieson, chief of gynecology and obstetrics for Emory Healthcare in Atlanta.

According to the 2012 Census, 75.4 million U.S. women were of childbearing age, defined as 15 to 50 years old. Currently, pregnant women are recommended to take flu and whooping cough vaccines and certain others depending on individual circumstances, but none of these have been specifically tested and proven safe for pregnant women.

“We have an enormous number of women of childbearing age and potentially getting pregnant, and what’s the safest vaccine for them?” said Dr. Larry Corey, a vaccine expert at Fred Hutchinson Cancer Center in Seattle who is helping oversee vaccine trials conducted by Moderna and other drugmakers in collaboration with the U.S. government.

Doctors may want to see even more data for completely new vaccine technologies, such as those used by Moderna and Pfizer, compared with one that has already been used in pregnant women.

Such differences highlight why “we need multiple vaccines” to best address the needs of specific populations, Corey said.

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