In February 2021, Pfizer launched a randomized, placebo-controlled, observer-blind study to evaluate the safety of its COVID-19 shot — BNT162b2 — in healthy pregnant women.

The injections were set to take place between 24 and 34 weeks gestation, with participants randomized 1-to-1 to receive a COVID-19 shot or placebo.

The study was initially set to enroll 4,000 women, but Pfizer only signed up 349, then stopped enrollment entirely.

The Centers for Disease Control and Prevention’s (CDC) widespread endorsement of COVID-19 shots for pregnant women before the study was completed may have negated the need for the trial.

Pfizer stated that because so many pregnant women had already gone ahead and gotten the shot, due to the government’s endorsement, enrollment dropped and there was no reason to move ahead with the study.

No randomized trial data are available for use of the COVID-19 shot in pregnant women, and Pfizer cut its pregnancy trial short.

But this doesn’t stop the CDC from recommending COVID-19 injections for everyone 6 months and older, including “people who are pregnant, breastfeeding, trying to get pregnant now, or those who might become pregnant in the future.”