As Americans get vaccinated, fewer are getting tested for coronavirus, which doctors say could be a big problem

Public heath experts have been critical of states such as Texas and Mississippi that tossed aside mask mandates  last week at a critical juncture in the nation's pandemic.

They also warn of another threat to hard-fought gains in recent weeks – the number of Americans getting tested for coronavirus has dropped significantly since January.

Though the testing slowdown may be the result of fewer infections, it also might signal too many Americans are growing complacent as the second year of COVID-19 marches on and millions get vaccinated every week.  

Testing remains a staple of the effort to control COVID-19, along with wearing masks, social distancing, avoiding crowded indoor places and hand hygiene. Though officials are optimistic vaccines will offer protection, some warn the nation might be letting its guard down before enough Americans are protected from the virus.

"A lot of people are just kind of done with the pandemic," said Mary Hayden, professor of internal medicine and pathology at Rush Medical College in Chicago.

In January, labs and other testing sites completed an average of nearly 1.9 million tests each day as cases reached record levels. Average daily testing dropped to 1.5 million in February and 1.3 million in March, according to figures from the COVID Tracking Project. 

Hayden said the nation's testing never reached levels that public health officials thought were "adequate or optimal" to control the virus.

"We never quite got there," said Hayden, an Infectious Diseases Society of America fellow. "And now we’re dropping."

Testing declines, social distancing eases

Testing was hard to get when the first major outbreaks emerged last spring in metro Seattle and New York. The nation slowly built capacity with private labs, and now the United States can test more than 2 million each day.  

This slump is not the first time Americans have sought fewer tests. In the summer, testing dropped in several Southern states before cases came roaring back. 

Daily cases still surpass levels of late summer and fall, but it's likely that fewer people were exposed to the virus in recent weeks compared with January's peak. That means fewer people experience symptoms that compel them to get tested.

As the pandemic rolls into year two, people are less willing to get screened for the virus, Hayden said. Earlier in the pandemic, people sought testing even if they had no symptoms or mild symptoms because they were worried about the virus. Based on anecdotal reports, it seems fewer nonsymptomatic people are getting tested, she said.

Another factor: public health agencies are focusing limited resources on getting more Americans vaccinated. Former large testing sites, such as Dodger Stadium in Los Angeles and State Farm Stadium near Phoenix, have converted to mass vaccination sites. 

As testing wanes, public health officials are worried about moves by state government to ease social distancing. 

Governors in Alabama, Mississippi, Texas, Montana and Iowa declared masks are no longer required to prevent the spread of COVID-19. Of those five states, Johns Hopkins University data shows, only Montana's ratio of positive tests over the past week is less than 5%, the threshold the World Health Organization recommends before reopening.

Although local governments and private businesses can make their own choices about wearing masks in public places, such as restaurants, eliminating state mask mandates  and allowing more people to gather indoors undermines virus control strategies that have been pivotal in reducing spread of COVID-19, said Romney Humphries, a Vanderbilt University Medical Center professor of pathology, microbiology and immunology.

She said relaxing social distancing contributes to "an overall culture of the pandemic is winding down" and may convince some people testing is less important.

"All of those things are creating a sense for the public that the pandemic is over," Humphries said. "By no means is that true."

Only 21% of adults had received at least one dose of vaccine as of Thursday, according to the Centers for Disease Control and Prevention. Four out of five U.S. adults have not been vaccinated. 

Those who received just one dose of the Pfizer-BioNTech or Moderna vaccine are not fully protected. Now that the single-dose Johnson & Johnson vaccine is bolstering the nation's vaccine supplies, President Joe Biden said there should be enough doses for every American by the end of May. 

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Dr. Rebecca Weintraub, an assistant professor at Harvard Medical School's Department of Global Health and Social Medicine, said people are not fully protected until two weeks after they get both doses of the Pfizer-BioNTech or Moderna vaccines.

Although early data is positive, it's not known whether the vaccine prevents spread of the virus from an immunized person to others.

"What we do know is the virus is circulating in our communities," Weintraub said. "And so one of the most effective ways to understand, either am I infected or could I be infected, is to get tested."

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The College of American Pathologists said members noted a "significant decrease" in the number of tests at health care institutions nationwide.

In metro Seattle, testing has dropped in tandem with new cases. At the University of Washington's lab, tests surged in the late fall. Tests are about half of fall's peak, said Geoffrey Baird, the university's acting chair of laboratory medicine and pathology.

The vaccine rollout is a pivotal period that Baird and others are watching. If vaccination efforts slow, more states relax mask mandates and virus variants gain traction, it could lead to another big spike in cases, Baird said.

"All of us in the testing business are wondering what will occur in the coming month or two," he said. 

Hayden said the public must remain vigilant, even as more and more people get vaccinated. 

"While the infection rates are much lower, they are still high," Hayden said. "I don’t think we're at a place yet where we can really relax our overall strategies and reduce testing." 

Contributing: Karen Weintraub

Contact Ken Alltucker at alltuck@usatoday.com