CDC’s Covid-19 mask mandate clouded by flawed data
The Centers for Disease Control and Prevention is fighting Covid-19 without a full arsenal of data that some public health experts have said should be persuaded more people to take action to contain the pandemic.
When CDC director Rochelle Walensky said last week that people should once again wear masks indoors in areas with “substantial” levels of Covid-19 transmission, for example, she said that evidence shows that the Delta variant could be spread just as easily by vaccinated people who are infected as by unvaccinated people. The CDC has pointed the finger at Provincetown, Massachusetts, where it said large gatherings in July at bars, nightclubs and house parties led to hundreds of Covid-19 infections. Other studies published over the weekend supported the CDC’s finding, Dr Walensky said.
The data from Provincetown contained two startling details: Almost three-quarters of those infected were fully vaccinated, the CDC said, and samples showed that the amount of people infected with the virus carried – or viral load – was similar between vaccinated and unvaccinated patients. The CDC concluded from the latter that vaccinated people who were infected could spread the Delta variant as easily as the unvaccinated.
The significance of some viral load data has been disputed. Some officials within the CDC disagree with the agency’s conclusion that vaccinated people who are infected can spread the virus as easily as unvaccinated people, and argue that more testing needs to be done, including including tests that measure the degree of contamination of viral particles, according to a person familiar with the subject.
“There is no direct relationship between a high viral load and infectivity, but we always make decisions based on imperfect data,” said Tom Frieden, who led the CDC from 2009 to 2017.