Pfizer Study of Covid-19 Vaccine in Pregnant Women Delayed by Slow Enrollment

Changing guidelines and the possibility of being given a placebo made the trial unappealing to some expectant mothers. fizer closed enrollment at many U.S. sites this summer, after fewer than expected numbers of subjects entered the study, researchers say. The slow enrollment was driven by revised guidelines from government and physician groups that recommend pregnant women receive the shots based on new real-world research, according to trial-site researchers. They also say increased vaccine supply made a trial that included the possibility of being given a placebo instead of a vaccine unappealing to expectant mothers and raised questions about the ethics of seeking volunteers.