Do Covid vaccines prevent you from spreading the virus or just protect you from getting sick?
Scientists still don’t know – and uncertainty has big implications during vaccine launches.
Pfizer and Moderna, the companies that have developed vaccines authorized in the United States so far, say their vaccines are about 95% effective in preventing diseases with Covid’s symptoms. But there is still insufficient evidence on whether vaccines also prevent infection and asymptomatic transmission.
The companies say research is underway to determine the answer. Without vaccines, research suggests that asymptomatic transmission of the coronavirus that causes Covid is responsible for about a quarter of infections.
The result, experts say, is that care such as wearing masks, social distance and avoiding crowded spaces will be necessary until the country approaches herd immunity, at which point enough people are immune to a disease to make it spread. unlikely. Some studies estimate that about 75% to 80% of the US population needs to be immune to Covid-19 to achieve collective immunity, but that number is a moving target and may increase as new variants emerge.