Pfizer has begun testing a pill for the prevention of COVID-19 among those who have been exposed to the virus.
The drug maker says it plans to study the pill in combination with a low dose of an HIV drug.
Those taking part in the study must to be at least 18 years old and live in the same house as someone with COVID-19.
Pfizer says it plans to enroll more than 2,500 people in the study.