The US study for pregnant women will cover around 4,000 women aged 18+, who will be vaccinated between 24 and 34 weeks of gestation. It will only include healthy women who are not at known risk of complications during pregnancy.
Two doses will be administered 21 days apart, as is the case with the vaccine for the general population.
The study will evaluate the safety, tolerability, and immunogenicity of the vaccine in pregnant women. It will also assess safety in infants of vaccinated pregnant women and the transfer of potentially protective antibodies to their infants. Infants will be monitored through approximately six months of age.
Pfizer and BioNTech have completed a developmental and reproductive toxicity (DART) study with BNT162b2, which was required by regulatory authorities before starting the study. Those studies showed no evidence of fertility or reproductive toxicity in animals.
Pfizer is currently trialling its vaccine candidates against Respiratory Syncytial Virus (Phase 3) and Invasive Group B Streptococcus Infection (Phase 2) in pregnant women; and says its experience will help inform the BNT162b2 study.
William Gruber M.D., Senior Vice President of Vaccine Clinical Research and Development, Pfizer, said: “Pregnant women have an increased risk of complications and developing severe COVID-19, which is why it is critical that we develop a vaccine that is safe and effective for this population. We are deeply thankful to the volunteers who are enrolling in the trial, and site investigators who are leading this work.”
The vaccine in children
First authorized in the UK on December 2, the vaccine BNT162b2 has now been granted authorization in more than 50 countries worldwide. In the US, the vaccine is authorized under an Emergency use Authorization (EUA) for adults aged 16+, and could gain full Biologics License Application approval this year.
Pfizer and BioNTech also plan to embark on additional studies in children aged 5-11 years old in the coming months; joining AstraZeneca which launched a study for children aged 6-17 last week.
Pfizer/BioNTech plan to then progress their studies to cover children younger than five years old later this year: although they have not specified exactly which age groups this will cover.
Safety and efficacy of the Pfizer/BioNTech vaccine in teenagers aged 12 - 15 years are already being evaluated in a global Phase 3 study (C4591001) and the relevant data are planned to be submitted to the regulatory authorities in the second quarter of 2021.
The companies are also planning studies to further evaluate the vaccine in people with compromised immune systems.