How was the exposure to covid monitored? Were both groups exposed to the same people. How do you know who of those people the groups were exposed to did or didn't have covid? Unless both groups received the same exposure to covid cases then how is the calculated effectiveness accurate?
How was the exposure to covid monitored? Were both groups exposed to the same people. How do you know who of those people the groups were exposed to did or didn't have covid? Unless both groups received the same exposure to covid cases then how is the calculated effectiveness accurate?