In any case, the immune defenses initiated by the vaccines should recognize the virus soon after infection and destroy it before significant damage occurs.
“This is what explains why people get infected and why people don’t get seriously ill,” said Michel C. Nussenzweig, immunologist at Rockefeller University in New York. “It’s almost inevitable, unless you give people very frequent reminders.”
There is limited evidence beyond anecdotal reports to indicate whether breakthrough infections with the Delta variant are more common or more likely to spread to other people. The CDC has recorded about 5,500 hospitalizations and deaths among those vaccinated, but it does not track milder breakthrough infections.
Additional data is emerging from the Covid-19 Sports and Society Workgroup, a coalition of professional sports leagues that work closely with the group’s CDC Sports teams testing more than 10,000 people at least daily and sequencing all infections, according to Dr. Robby Sikka, a doctor who worked with the Minnesota Timberwolves in the NBA.
Revolutionary infections in the leagues appear to be more common with the Delta variant than with Alpha, the variant first identified in Britain, he said. As might be expected, the vaccines dramatically reduce the severity and duration of the disease, with players returning less than two weeks after being infected, up from nearly three weeks earlier in the pandemic.
But while sick, players carry very large amounts of the virus for seven to ten days, compared to two or three days in people infected with Alpha, Dr Sikka said. Infected players are required to quarantine themselves, so the project could not determine if they have spread the virus to others – but it is likely that they would, he added. .
“If they are unwillingly reintegrated into society, I think you will spread from vaccinated individuals,” he added. “They don’t even recognize they have Covid because they think they are vaccinated.”