Pfizer Inc and its partner BioNTech plan to give volunteers who received a placebo in its Covid-19 vaccine trial an option to receive a first dose of the vaccine by March 1, 2021, while staying within the study.

The trial's Vaccine Transition Option allows all participants aged 16 or older the choice to discover whether they were given the placebo, "and for participants who learn they received the placebo, to have the option to receive the investigational vaccine while staying in the study," the companies said on their website for trial participants.

Trial participants who received the placebo will have two doses of the investigational vaccine reserved for them within the study, the companies said on the website.