Preliminary data from seven U.S. states show that the arrival of the Delta variant in July may be fueling a rise in breakthrough infections among the fully vaccinated.
At least 1 in every 5 new COVID-19 cases in six of these states have involved vaccinated people, with higher percentages of hospitalizations and deaths among these folks than had previously been seen in all seven states, The New York Times reported.
Still, the absolute numbers of vaccinated people made sick by COVID-19 remains very low, experts said, and the vaccines are still very potent weapons against severe disease.
If breakthrough infections are becoming more common, "it's also going to demonstrate how well these vaccines are working and that they're preventing hospitalization and death, which is really what we asked our vaccines to do," said Anne Rimoin, an epidemiologist at the University of California, Los Angeles, told the Times.
Importantly, a vast majority of vaccinated people who are hospitalized for COVID-19 are likely to be older adults or those who have weakened immune systems. CDC data show that 74% of breakthrough cases are among adults aged 65 or older.
The numbers suggest that people who are at higher risk for complications from COVID-19, and anyone who lives with a high-risk person, "really needs to seriously consider the risks that they're taking now," Dr. Dean Sidelinger, a state epidemiologist and state health officer for Oregon, told the Times.
"Remember when the early vaccine studies came out, it was like nobody gets hospitalized, nobody dies," Dr. Robert Wachter, chairman of the department of medicine at the University of California, San Francisco, told the Times. "That clearly is not true."
"If the chances of a breakthrough infection have gone up considerably, and I think the evidence is clear that they have, and the level of protection against severe illness is no longer as robust as it was, I think the case for boosters goes up pretty quickly," Wachter added.
The seven states analyzed by the Times — California, Colorado, Massachusetts, Oregon, Utah, Vermont and Virginia — were chosen because they are keeping the most detailed data, the Times said. It is not certain whether the trends in these states would hold across the country.
The increases seen are largely due on the mathematics of mass vaccination: Scientists have always expected that as the number of vaccinated people exponentially grows, vaccinated people will show up more frequently than before in tallies of the severely ill and dead.
"We don't want to dilute the message that the vaccine is tremendously successful and protective, more so than we ever hoped initially," said Dr. Scott Dryden-Peterson, an infectious disease physician and epidemiologist at Brigham & Women's Hospital in Boston. "The fact that we're seeing breakthrough cases and breakthrough hospitalizations and deaths doesn't diminish that it still saves many people's lives."
The U.S. Centers for Disease Control and Prevention had no comment on the states' numbers, but the agency is expected to discuss breakthrough infections, hospitalizations and vaccine efficacy during a news briefing on Wednesday, the Times reported.
The states' data do confirm that vaccinated people are still far less likely to become severely ill or to die from COVID-19. In California, the 1,615 hospitalizations of people with breakthrough infections as of Aug. 8 represents just 0.007% of nearly 22 million fully immunized residents, and breakthrough deaths constitute an even smaller portion, the Times reported.
But in six of the states, breakthrough infections accounted for 18% to 28% of recorded cases in recent weeks, the newspaper said. These numbers are likely to be low, because most fully immunized people may not feel ill enough to seek a test.
Breakthrough infections accounted for 12% to 24% of COVID-19 hospitalizations in the states, the Times found. The number of deaths was too small to arrive at a solid number, although it does appear to be higher than the CDC estimate of 0.5%.
The latest numbers make a good case for booster shots, and a recent survey showed that seniors can't wait to get one: Among vaccinated Americans, 72 percent of those who are 65 or older already say they want a booster shot.
U.S. to Recommend Booster Shots for Most Americans
The Biden administration plans to recommend that most Americans get a booster shot eight months after they received their second dose of either the Pfizer or Moderna COVID-19 vaccines, as the highly infectious Delta variant marches across the country.
Officials could announce the decision as early as this week, with third shots becoming available to those most vulnerable as early as mid-September, the Times reported.
People who chose the single-dose Johnson & Johnson vaccine will likely also need a booster shot, but officials are waiting for the results of the company's two-dose clinical trial that are expected later this month.
The first boosters will be given to nursing home residents, health care workers and emergency workers. Next up would be older people who were near the front of the line when vaccinations began late last year, followed by the general population. The plan is to give people the same vaccine they first received, the Times reported.
What has U.S. health officials worried? Data from Israel continues to suggest that the Pfizer vaccine's protection against severe disease has fallen significantly for elderly people who got their second shot in January or February, the Times reported.
The latest data, posted on the Israeli government's website on Monday, shows a continued erosion in the potency of the Pfizer vaccine against mild or asymptomatic infections in general and against severe disease among seniors who were vaccinated early in the year.
One slide suggested that for those 65 years or older who got their second shots in January, the vaccine is now only about 55 percent effective against severe disease. But researchers noted the data has a wide margin of error, and some said other Israeli government data suggested the decline in efficacy was less severe, the Times reported.
"It shows a pretty steep decline in effectiveness against infection, but it's still a bit murky about protection against severe disease," said Dr. Peter Hotez, a vaccine expert at the Baylor College of Medicine in Houston who reviewed the data, told the Times.
Dr. Jesse Goodman, a former chief scientist with the U.S. Food and Drug Administration, said the data shows "worrisome trends" that hint at waning efficacy. But he told the Times that he would like to see more detail from Israel and data indicating whether the United States is headed down the same road.
Federal officials said the U.S. booster program will almost certainly follow the same scenario as the initial vaccination program, the Times said. The first shots for the general public in the United States were administered on Dec. 14, days after the FDA. authorized the Pfizer shot for emergency use. People started receiving the Moderna vaccine a week later.
The regulatory path for additional shots is not entirely clear. Pfizer filed data to the FDA on Monday that it said showed the safety and effectiveness of a booster shot, but the data was preliminary. Moderna is also exploring the safety and efficacy of both a half-dose and a full dose as a third shot.
About 60% of the U.S. population has gotten at least one dose and nearly 51% are fully vaccinated, according to the U.S. Centers for Disease Control and Prevention. That, in turn, has caused a shortage of intensive care unit beds, nurses and other front-line staff in areas that can no longer keep up with the flood of unvaccinated patients.
"That's heartbreaking, considering we never thought we would be back in that space again," Dr. Francis Collins, head of the National Institutes of Health, said on Fox News Sunday. "But here we are with the Delta variant, which is so contagious, and this heartbreaking situation where 90 million people are still unvaccinated who are sitting ducks for this virus, and that's the mess we're in. We're in a world of hurt."
In the meantime, the World Health Organization — citing a lack of global supply of vaccines — has objected to richer nations moving ahead with booster shots when citizens of many poorer countries have yet to receive even a first dose of vaccine.