The study recruited 3,950 health workers, emergency responders and others at high risk of infection. Participants washed their noses weekly and sent in the samples for testing, allowing federal researchers to track any infections, symptomatic or not. Two weeks after vaccination, the vast majority of people vaccinated remained virus-free, according to the study.
Follow-up data from clinical trials support this finding. In results released by Pfizer and BioNTech on Wednesday, for example, 77 people who received the vaccine had coronavirus infection, compared to 850 people who received a placebo.
“Obviously, some vaccinated people are infected,” said Dr Duprex. “We are stopping the symptoms, we are preventing people from entering hospitals. But we don’t make them completely resistant to infection. “
The number of vaccinated infected people is likely higher among those who receive vaccines made by Johnson & Johnson and AstraZeneca, which have lower efficacy, experts said. (Still, these vaccines are worth taking because they consistently prevent serious illness and death.)
Infection rates may also be higher in people exposed to a variant of the virus that can bypass the immune system.
Cases across the country are once again on the rise, threatening a new wave. Dr Walensky’s comment came just a day after he made an emotional appeal to the American public to continue to take precautions.
“I ask you to hold on a little longer, to get yourself vaccinated when you can, so that all of these people we all love are still there when this pandemic ends,” she said.