Lingering questions about COVID-19 transmission and immunity are clouding the outlook for the fall as the U.S. drops restrictions, including mask requirements, and reduces case surveillance.

The decisions to forgo some protective measures have split public health experts as the virus surges in some countries overseas and vaccination slows within the United States. New federal guidance lifting indoor mask recommendations for vaccinated people is also prompting a number of Republicans to flout mask mandates altogether, with some state leaders going so far as to ban masks in schools.

Cases will likely increase after the summer as people move indoors, said Ali Mokdad, a professor at the University of Washington’s Institute for Health Metrics and Evaluation. But the severity of outbreaks as the weather cools will depend on the circulation of variants and how many people get vaccinated in the coming months. 

“The rise depends on how well we do in addressing vaccine hesitancy and if new escape variants are circulating,” Mokdad said in an email. 

The combination paints an uncertain future as scientists try to determine how long immunity lasts. Researchers don’t yet know whether the public will need booster shots or whether future variants could undercut the vaccines. 

Older adults, the most vulnerable to the virus, are also the least likely to maintain long-term immunity. Because the elderly were among the first groups vaccinated last winter, they’re also the ones facing the earliest test of the vaccines’ longevity.

New cases overall are at their lowest since June 2020, with the seven-day U.S. average below 20,000. Recent studies show the current vaccines have ample, if diminished, protection against current variants.

Infection after vaccination

But documented breakthrough cases, while rare, can cause transmission. The New York Yankees made headlines last month when nine people, all fully vaccinated with a Johnson & Johnson shot, tested positive.

Neither the Yankees nor the New York Health Department answered questions about the outbreak. But the Johnson & Johnson shot is around 66 percent effective at blocking COVID-19 illness — compared with a 94 percent or better efficacy rate for Moderna’s or Pfizer’s vaccines.

The incident highlights the risk of infection after vaccination, particularly with the Johnson & Johnson shot, even if it successfully wards off serious illness.

On May 20, senior Food and Drug Administration official Peter Marks said the incident was “not totally shocking,” citing the J&J vaccine’s lower efficacy.

“I don’t want this to start a controversy, but there could be a dialogue about the mask-wearing and the wisdom of mask-wearing, and that’s why I tell people if you still feel comfortable wearing a mask, you should wear a mask,” he said. “If you feel uncomfortable wearing a mask, follow the CDC guidance.”

Reversal sparks frustration

The new Centers for Disease Control and Prevention mask recommendations sparked a backlash for allowing vaccinated people to abandon masks in most indoor settings, regardless of community case levels and vaccination rates or the type of shot a person received. The abrupt reversal left many state and industry leaders frustrated about the lack of direction or time to prepare. 

Just 10.6 million Americans received Johnson & Johnson’s one-shot vaccine because of a debacle at a facility run by contractor Emergent BioSolutions. Epidemiologists have more confidence in Pfizer’s and Moderna’s ability to block transmission, although studies largely were performed while the world was under mask restrictions. 

Jeanne Marrazzo, director of the Division of Infectious Diseases at the University of Alabama at Birmingham, on May 20 said the studies, including a real-world analysis from Israel, probably reflected varying degrees of mask compliance. 

Meanwhile, the country’s largest nurses union raised questions about the studies underlying the CDC’s swift about-face. According to a review by National Nurses United, many of the studies that CDC cites in its science brief behind the change are preprints that were not vetted by experts. NNU President Zenei Triunfo-Cortez said she was “pretty shocked” by the guidance.

Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, agrees there is not enough science on how well the vaccines curb transmission.

“I found this a little confusing … not because I don’t believe these vaccines are really, really powerful tools. They are. But the data that was put forward, frankly, was pretty obtuse,” he said.

The CDC did not respond to requests for comment, but Director Rochelle Walensky defended the agency’s rationale at a U.S. Chamber of Commerce event on May 27.

“There have been evolving data that have said if you are vaccinated, even if you have a mild infection, you can’t get infected and bring it home to somebody else,” she said.

Debate over mask bans

The CDC guidance prompted some Republican lawmakers to boycott the ongoing mask mandate of Speaker Nancy Pelosi, although many decline to say whether they’re vaccinated. Federal health officials said the guidelines are being misinterpreted as giving unvaccinated people the OK to drop masks too.

Some GOP-led states, such as Iowa and Texas, banned mask mandates in schools, although no vaccine is authorized for children under 12 and the CDC guidance said school mask-wearing should continue for the remainder of the academic year. The CDC is expected to update recommendations for the 2022-23 school year within weeks.

Another dispute with teachers unions may be coming. The American Federation of Teachers recently endorsed a full reopening in the fall, but the CDC’s guidance is prompting questions.

“With the school year ending within weeks, we had hoped to have the time this summer to prepare and incorporate any new COVID-19 guidance into our back-to-school plans,” AFT President Randi Weingarten said in a letter, voicing concerns about state mask bans and forcing teachers to be the “mask police.”

The new guidance also bolstered calls to toss long-awaited workplace protection rules from the Occupational Safety and Health Administration.

Rep. Virginia Foxx, R-N.C., led House Education and Labor Committee Republicans in a May 24 letter to Labor Secretary Marty Walsh, saying that an emergency temporary standard would be “unnecessary, ill-timed, and sweeping.”

But proponents say masks are important for workers.

Unlike customers, “many workers spend 8-12 hours a day at work with frequent or prolonged close contact with each other or the public in poorly ventilated indoor settings,” former OSHA officials David Michaels and Jordan Barab wrote in Time.

Less monitoring of cases

Amid all of this, the CDC recently stopped monitoring breakthrough infections unless they result in hospitalization or death. Walensky said the agency has limited resources and should prioritize severe cases.

Testing rates also have fallen by a third since January, suggesting some cases could be missed.

Only up to 10 percent of positive test results were being sequenced to monitor the spread of variants in May, Walensky said. The administration is stepping up genomic surveillance through a $1.7 billion infusion from the recent COVID-19 aid law.

CDC data released on May 25 found that of 555 test samples in breakthrough cases from January through April, 64 percent were caused by variants of concern. 

By April 30, CDC had tracked 10,262 breakthrough infections in vaccinated people across 46 states, a fraction of the 101 million fully vaccinated people in the U.S. by then.

But this number may be a “substantial undercount,” researchers acknowledged.

To some experts, the move to tracking only serious breakthrough cases makes sense. 

“The goal of these vaccines is to keep people out of the hospital … and out of the morgue,” said University of Pennsylvania vaccinologist Paul Offit.

But Marrazzo called current genomic sequencing capabilities “tenuous,” even while acknowledging breakthroughs appear rare.

“I understand it,” she said of the decision to scale back surveillance, “but it does make me concerned that it’s going to be part of a lost opportunity to really track vaccine failure in a setting of variant evolution over time — and reduced mask-wearing.”