The study will follow participants for up to one year to find out how long vaccine protection lasts against Covid-19 and new variants. https://ift.tt/3BpFj78 https://ift.tt/2YyKfZp World New York Times October 9, 2021 at 08:00PMPfizer to vaccinate entire city in Brazil as part of study.

By Adeel Hassan from NYT World https://ift.tt/3BpFj78
https://ift.tt/3BpFj78 https://ift.tt/2YyKfZp New York Times