In this July 22, 2020 file photo, health care workers use a nasal swab to test a person for Covid-19 at a pop up testing site at the Koinonia Worship Center and Village in Pembroke Park, Florida. 
In this July 22, 2020 file photo, health care workers use a nasal swab to test a person for Covid-19 at a pop up testing site at the Koinonia Worship Center and Village in Pembroke Park, Florida.  Joe Raedle/Getty Images

Continued testing is “critically important” in the fight against Covid-19, according to the US Centers for Disease Control and Prevention, especially as cases plateau and more contagious variants spread around the US.

However, Covid-19 testing in the US has dropped by a quarter since reaching a peak in mid-January, according to data from The COVID Tracking Project. 

“Widespread testing must continue in order to defeat the pandemic,” Dr. Greta Massetti, lead for the CDC COVID-19 Emergency Response Community Interventions and Critical Populations Task Force, told CNN. “It will take many months for all Americans to have the opportunity to receive one of the vaccines available. In the meantime, it’s essential that people continue to take preventive measures.”

Daily Community Profile Reports from the White House Covid-19 team have been tracking various indicators including testing and color-code metrics based on transmission severity.

In terms of testing rates, a seven-day daily average of at least five tests for every 100 people is ideal. But in the latest report published Tuesday, only five states reached that threshold over the last seven days, landing them in the “dark green” category: Rhode Island, Vermont, Massachusetts, New York and Alaska.

Meanwhile, eight states were in the “red” or “dark red,” with less than one test for every 100 people: Oklahoma, Missouri, South Dakota, Mississippi, New Hampshire, Washington, California and Georgia. 

The federal report notes that the number of tests “may be underestimated due to delayed reporting,” but nearly every state had a significant decline in testing rates compared to mid-January.

California has had one of the largest drops in testing since mid-January, federal data shows. According to the state health department, testing volume has decreased for the fifth straight week — down from a seven-day average of about 230,000 tests per day to about 181,000 tests per day. In conversations with testing laboratories, the state found that the decrease was driven by less frequent utilization of testing services, not by lack of supply or capacity. 

In fact, national data from Quest Diagnostics shows that the lab processed about 4.3 million diagnostic Covid-19 tests in February, but had the capacity to process up to 7 million.

Overall, federal data shows that the median turnaround time for Covid-19 tests had dropped to one day in nearly every state. For about a dozen states, that’s an improvement from the two or three day turnaround times in mid-January.

California recently released guidance around testing for Covid-19 during the vaccine rollout, urging residents to continue to get tested even if they’ve been fully vaccinated.

“If your job requires it, you still need to get tested regularly, even if you’ve had the vaccine,” the state’s Covid-19 website states.