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The arrival of Covid-19 vaccines at the hospital where I work felt like a glimmer of hope, a small reprieve from the daily anxiety of feeling exposed and vulnerable while taking care of patients.

When the time came for my appointment, though, I wavered. As a physician, I understand and respect the privilege of being among the first group in the United States to be offered the vaccine. But as a pregnant woman, I was left trying to interpret vague guidelines developed without data from clinical trials about people like me. I ultimately decided to get the vaccine, like other pregnant health care workers, despite feeling anxious about making this decision without adequate information about its effectiveness and safety for both me and my baby.


The first Covid-19 vaccine trials excluded pregnant people, as do most clinical trials, ostensibly to protect against possible unknown harms to the person or fetus. The FDA also requires additional testing in order to study a treatment in pregnancy, so excluding pregnant people becomes a matter of expediency. However, the default of excluding pregnant people from clinical trials forces them to make treatment decisions without necessary information.

The announcement on Thursday that Pfizer/BioNTech will conduct a trial of their vaccine in pregnant people is good news, but it won’t help those who are getting vaccinated now.

The World Health Organization recently clarified its stance on Covid-19 vaccination in pregnant people, but its current language still falls short of recommending it. Other published recommendations have been similarly ambivalent, such as the American College of Obstetricians and Gynecologists recommendation that “vaccines should not be withheld from pregnant individuals.” The Centers for Disease Control and Prevention’s website offers this cautious guidance:


“Based on current knowledge, experts believe that mRNA vaccines are unlikely to pose a risk to the pregnant person or the fetus because mRNA vaccines are not live vaccines. … However, the potential risks of mRNA vaccines to the pregnant person and the fetus are unknown because these vaccines have not been studied in pregnant people.”

Choosing to be vaccinated against Covid-19 without an affirmative recommendation to do so made me feel vulnerable, not protected. But it doesn’t have to be that way for others. The nation has an opportunity to study the safety and efficacy of the vaccine in the pregnant health care workers who are choosing to get it now. But I’m afraid that opportunity is being lost without a systematic effort to track them.

When I got my Covid-19 vaccine, I was instructed to scan a QR code on a poster. Doing that brought me to V-safe, a vaccine safety tracking system from the CDC. One of the questions I answered with each dose was, “Were you pregnant at the time of your Covid-19 vaccination?” to which I answered “Yes,” fully expecting to be asked a series of other questions about my pregnancy. I wasn’t.

Instead, I only answered routine questions about arm soreness, fatigue, and fever. I waited for an email or phone call inviting me to enroll in a study of pregnant people receiving the vaccine. Instead, silence. Why is nobody asking us for more information?

Randomized clinical trials like the Pfizer/BioNTech one, in which some volunteers are randomly assigned to receive a treatment and some are not, are the gold standard for studying new medical therapies. But there’s another way to get useful, timely information about the intersection of Covid-19 vaccination and pregnancy. The cadre of pregnant health care workers already receiving the vaccines makes a natural cohort, a group of people with a certain exposure who could be followed over time for outcomes of interest like antibody formation, Covid-19 infection, and pregnancy complications.

This kind of observational study would not provide the kind of information generally required for formal FDA approval of a drug or vaccine, but it would deliver meaningful information to pregnant individuals and their providers who need to make decisions about the vaccine now. Searching high and low for such a study, I found one grant recently issued to researchers who plan to begin tracking individuals who were vaccinated against Covid-19 during pregnancy for adverse outcomes over a five-year period.

I know several pregnant health care workers who have already received Covid-19 vaccines. I can only imagine how many thousands of us there are across the nation’s health systems. We were put in the position of choosing to be vaccinated without data, but those who come after us don’t have to be.

The CDC already has systems in place to monitor vaccine safety, and should leverage this national infrastructure to go beyond basic adverse-event reporting for pregnant health care workers who are now getting vaccinated against Covid-19. People like me could be providing vital, timely data on the vaccine in pregnancy if only there were a system in place to do so.

Health care workers make great study participants. Really. Just ask us to sign up.

Catherine Mezzacappa is an internal medicine resident physician at Yale New Haven Hospital with a background in public health research. The opinions presented here are hers and not necessarily those of her employer.

Hear Mezzacappa talk more about vaccinations and pregnancy on an episode of the “First Opinion Podcast.”

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