Ever since Americans started rolling up their sleeves on coronavirus vaccines, health officials have said that people who are vaccinated are very unlikely to become infected or suffer from serious illness or death. However, preliminary data from seven states suggest that the arrival of the Delta variant in July may have changed the calculation.

Breakthrough infections in vaccinated individuals accounted for at least one in five newly diagnosed cases in six of these states and higher percentages of total hospital admissions and deaths than previously seen in any of them, according to figures compiled by the New York Times.

However, the absolute numbers remain very low and there is no doubt that the vaccines continue to provide effective protection. This is still “a pandemic of the unvaccinated”, as the federal health authorities have often said.

Still, the trend marks a change in how vaccinated Americans rate their risks.

“Remember when the early vaccine studies came out, it was like no one was hospitalized, no one died,” said Dr. Robert Wachter, chairman of the medical school at the University of California at San Francisco. “That is clearly not true.”

The numbers support the belief, widely held by Biden government officials, that some Americans could benefit from booster vaccinations in the coming months. Federal officials plan to approve additional shots as early as mid-September, though it’s not clear who will receive them.

“If the chances of a breakthrough infection have increased significantly, and I think the evidence is clear and the protection against serious illnesses is no longer as robust as it used to be, I think the case for boosters is rising quite a bit.” Fast, ” said Dr. Guardian.

The seven states – California, Colorado, Massachusetts, Oregon, Utah, Vermont, and Virginia – were examined because they have the most detailed data. It is not certain that the trends in these states apply to the entire United States.

In any case, scientists have always expected that the number of people who have been vaccinated will become more and more represented in the census of the seriously ill and the dead as the population grows.

“We don’t want to water down the message that the vaccine is hugely effective and protective, more than we initially hoped,” said Dr. Scott Dryden-Peterson, an infectious disease physician and epidemiologist at Brigham & Women’s Hospital in Boston.

“The fact that we are seeing groundbreaking cases and groundbreaking hospital admissions and deaths doesn’t detract from the fact that it still saves many people’s lives.”

The CDC declined to comment on the states’ numbers. The agency is expected to hold a press conference on Wednesday to discuss breakthrough infections, hospital admissions and vaccine effectiveness.

Most breakthrough infection analyzes have numbers collected through the end of June. Based on the cumulative numbers, the CDC and public health experts concluded that breakthrough infections are extremely rare and that vaccinated people are most unlikely to get seriously ill.

State data shows that vaccinated people are much less likely to get seriously ill or die of Covid-19.