Just 1,345,064 travelers were screened at U.S. airports on Tuesday, the lowest since May 18 when 1,408,017 were screened, the TSA said.

United CEO Scott Kirby said Monday he thinks holiday travel will return to normal.

-ABC News' Sam Sweeney

San Diego has become the first county in the U.S. to declare that health misinformation is causing a public health crisis in its community. This follows the County Board of Supervisors' 3-2 vote Tuesday night.

Changes to county strategy to combat the pandemic will include: labeling health misinformation and providing timely health information to counter it; modernizing public health communications; investigating in digital resources and training for health practitioners and health workers; and developing a website to be a central resource for fighting health misinformation.

The new policy was introduced when 96.7% of hospitalizations in San Diego County were residents who were not fully vaccinated.

KISS co-lead singer Gene Simmons tested positive for COVID-19, the band shared on its Twitter page Tuesday evening.

In a statement, the band said the 72-year-old was experiencing "mild symptoms."

His diagnoses comes less than a week after co-lead singer Paul Stanley, 69, tested positive for COVID-19 as well.

In a statement released on Aug. 26, the band said that, "everyone on the entire tour, both band and crew, are fully vaccinated."

KISS has postponed four of its "End of the Road" tour shows from Sept. 1 to Sept. 5.

"The band and crew will remain at home and isolate for the next 10 days," the band said in a statement.

Peter Marks, the director of the Food and Drug Administration's Center for Biologics Evaluation and Research (CBER), announced the upcoming departure of two top vaccine regulators to his staff in an internal memo, which was obtained by ABC News.

Dr. Marion Gruber, director of the FDA's Office of Vaccines Research and Review (OVRR) and her deputy, Dr. Phil Krause, are set to leave the agency in October and November respectively, according to the memo.

Krause, who's been with the agency for over a decade, and Gruber, who has been with the FDA for over 30 years, were instrumental in the review and authorization of the three COVID-19 vaccines, the memo said.

The memo said that Gruber will be "retiring" and gave no other details about Krause's departure.

ABC News has reached out to both Gruber and Krause for comment.

When reached for comment about their departure, an FDA spokesperson told ABC News the agency is "confident in the expertise and ability of our staff to continue our critical public health work, including evaluating COVID-19 vaccines."

Their departures come at a critical time for the vaccine review team. After facing pressure to move as fast as possible to get vaccines' full licensure done, the agency is now weighing booster shots for a wider pool of Americans.

The timing of the booster shot approval has been a bone of contention amongst federal agencies after the Biden administration announced the availability of booster shots would begin ahead of any ruling from the FDA or Centers for Disease Control and Prevention advisory groups.

-ABC News' Sasha Pezenik

Dr. Paul Offit, a member of the U.S. Food and Drug Administration's vaccine advisory committee, said a two-dose COVID-19 vaccine "appears to be enough" to curb infection, rather than adding a booster shot.

"You look at states in the United States that have high immunization rates with a two-dose vaccine, it appears the two doses appears to be enough to be able to control this infection," Offit, who is also the director of the Vaccine Education Center at Children's Hospital of Philadelphia, told ABC News on Thursday night. "I think the critical issue here is not going to be boosting the vaccinated. I think if we really want to get on top of this pandemic, it's going to be about vaccinating the unvaccinated."

The FDA's vaccine advisory committee is set to hold a key meeting on COVID-19 vaccine booster shots on Sept. 17, just three days before the Biden administration plans to begin offering the shots to Americans.

"If the companies or the FDA can make a case that there has been an erosion in protection against severe critical disease and that that erosion in protection against severe disease would be mediated or eliminated by a third dose, then we could move forward," Offit said. "But to date, we really need to see those data to be able to make that decision."