Dr. Jerome Adams, the U.S. surgeon general under former President Donald Trump, slammed the U.S. Centers for Disease Control and Prevention over its change on isolation times for infected individuals.

In a Twitter thread, Adams criticized the agency's decision to omit the recommendation for COVID-19-positive individuals to take a COVID-19 test, prior to ending isolation.

The CDC reduced the isolation period from 10 days to five for asymptotic patients.

"Regardless of what CDC says, you really should try to obtain an antigen test (I know- easier said than done) and confirm it’s negative prior to leaving isolation and quarantine. There’s not a scientist or doctor I’ve met yet who wouldn’t do this for themselves/ their family," Adams tweeted.

The former surgeon general added, "This isn’t about the best science – it’s a compromise to keep the economy open in the face of inadequate tests."

-ABC News' Arielle Mitropoulos

The NFL and NFL Players Union agreed to new guidelines for when a player who is infected with COVID-19 can return to the field, according to ESPN.

Players who test positive can isolate for five days, in accordance with the new recommendations from the U.S. Centers for Disease Control and Prevention.

The agreement includes both vaccinated and unvaccinated players and is contingent on the players being asymptomatic, or at least demonstrating that their symptoms are resolving, after the five-day period, ESPN reported.

Under the current rules, unvaccinated players are required to isolate for 10 days when they test positive. Vaccinated players can return to the field as soon as they test negative.

The U.S. Centers for Disease Control and Prevention is investigating 86 cruise ships operating or planning to operate in U.S. waters that have reported COVID-19 cases.

In order to meet the threshold for a CDC investigation, a ship must report COVID-19 cases in more than 0.10% of passengers or have a single crew member test positive in the previous seven days.

The CDC started by investigating 38 ships, and has now investigated 48 additional vessels, which remain "under observation."

None of the ships have been designated as "red," which means they haven't reached the level of COVID-19 transmission needed to overwhelm the medical resources on board.

-ABC News' Mina Kaji

The U.S. Food and Drug Administration revealed new data on the efficacy of antigen tests for detecting the omicron COVID-19 variant.

The data so far suggests the tests do detect the variant, but they may have reduced sensitivity, the agency said.

The FDA and National Institutes of Health will continue to review the antigen tests' performance on the variant.

Last week, the CDC reported that omicron had overtaken delta to become the dominant COVID-19 variant in the U.S. However, on Tuesday, the CDC revised its initial estimates to noticeably lower numbers of omicron cases.

Last Monday, the CDC said omicron was estimated to makeup more than 73.2% of new cases as of Dec. 18. Now, the CDC says just 22.5% of new U.S. cases were estimated to be omicron as of Dec. 18. 

According to new data from this week, the CDC says omicron is now estimated to account for 58.6% of all new cases, officially making it the dominant strain in the U.S. In the New York and New Jersey region as well as the deep South, omicron is estimated to account for more than 85% of new cases. 

A CDC spokeswoman said in a statement, "There was a wide predictive interval posted in last week’s chart, in part because of the speed at which omicron was increasing. We had more data come in from that timeframe and there was a reduced proportion of omicron. It’s important to note that we’re still seeing steady increase in the proportion of omicron."

ABC contributor Dr. John Brownstein, an epidemiologist at Boston Children's Hospital, said, "It may be possible that a large portion of their [the CDC's] sequencing data had come from labs that were specifically looking for s-gene samples, thus falsely elevating the percent omicron in samples."

-ABC News' Arielle Mitropoulos