Massachusetts study: High viral load in infected vaccinated subjects

In the US state of Massachusetts, many people who were vaccinated were also infected with the corona virus at festivities. Experts attribute this to the delta variant – and recommend a mask requirement.

In the tourist town of Provincetown on the US peninsula Cape Cod, more than 900 coronavirus cases were registered after the national holiday on July 4th. Those affected came from a total of 23 US states.

The 469 infections among residents of the state of Massachusetts, in which Cape Cod is located, were examined more closely – with surprising findings: Almost three quarters of them were people who were fully vaccinated. This comes from a study by the US health authority Centers for Disease Control and Prevention (CDC). US virologists emphasize, however, that the likelihood that those who have been vaccinated will be infected with the Delta variant is still significantly lower than that of those who have not been vaccinated.

However, once vaccinated people have become infected, they seem to transmit the virus to the same extent as unvaccinated people. Because fully vaccinated people can carry almost the same viral load as unvaccinated people.

Delta variant – as infectious as chickenpox

Based on the investigation, the CDC recommended a return to masking requirements indoors – at least in the regions where the delta variant is widespread. This is as infectious as chickenpox. An infected person infects an average of five to nine people – at the beginning of the pandemic there were two to three people per infected person.

Criticism from other researchers

Experts agreed in principle with the CDC recommendations. But some, like Johns Hopkins University researcher Jennifer Nuzzo, pointed out that the Provincetown outbreak did not prove that vaccinated people were a significant source of new infections. The CDC recommendations are scientifically plausible, but not derived from the study.

Saskatchewan University virologist Angela Rasmussen said the method used in Provincetown to measure the viral load of people who had been vaccinated said nothing about whether the person infected others. The CDC said more data would be collected. Much larger studies have been carried out with tens of thousands of vaccinated and unvaccinated people.

“All caution to the wind”

Travis Dagenais is one of the vaccinated people in Provincetown who was found to be infected. He was one of the many who, trusting the vaccination protection, “dismissed all caution” and celebrated July 4th in the crowd. “The prevailing public message was that the vaccine was a return to normal,” the 35-year-old told the AP news agency. He reports a mild course of the disease with symptoms similar to colds. After a few days it was over.

With information from Sebastian Hesse, ARD-Studio Washington