As the debate over booster shots continues, public health officials are advising Americans not to get the additional vaccine doses until they are eligible—but a patchwork of eligibility criteria is forcing some doctors to determine which conditions qualify patients for boosters.

Are you ready for booster shots? Start thinking about these 6 factors now.

Health officials urge patience

In August, the Biden administration announced that it intended, beginning the week of Sept. 20, to make booster shots available for all Americans who received an mRNA vaccine eight months after their second shot, pending FDA authorization and CDC recommendation.

But last week, FDA's Vaccines and Related Biological Products Advisory Committee voted 16-2 against recommending booster shots of the Pfizer-BioNTech Covid-19 vaccine for all adults 16 and older six months after full vaccination. However, the committee unanimously voted to recommend the shots to adults 65 and older and those at high risk for severe Covid-19.

FDA is expected to make a decision regarding booster shots in the coming days and is not required to follow the recommendation of the advisory panel. CDC's Advisory Committee on Immunization Practices will also consider booster shot data this week.

Public health officials have said they believe booster recommendations are forthcoming. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said earlier this week he thinks "the real, proper regimen will turn out to be the original two shots plus a boost" for mRNA Covid-19 vaccines. And NIH Director Francis Collins agreed, saying, "Certainly, I think there will be a decision in the coming weeks to extend boosters beyond the list they approved on Friday."

In the meantime, Fauci urged Americans exercise patience and wait to get a booster shot until they're eligible, adding that there will be data on booster shots for Moderna and Johnson & Johnson vaccines soon.

Doctors left to determine who is eligible for booster shots

Currently, only patients with seriously compromised immune systems are eligible for a booster shot, including blood-cancer patients and those who have received an organ transplant or are taking immunosuppressants. CDC's list of qualifying patients also includes those with advanced or untreated HIV infection, those undergoing active cancer treatment, and those who recently received stem-cell transplants.

But some doctors say these criteria leave out other high-risk patients who may need a booster shot, like cancer survivors or those with a history of respiratory problems.

"There's a lot of gray area around how to define someone as moderately or severely immunocompromised," David Cohn, an oncologist and CMO at James Cancer Hospital, said. "You kind of have to set a bar somewhere."

While some health providers have started administering booster shots only to those eligible under CDC's criteria, others have been administering them to patients they believe to be high risk, the Wall Street Journal reports. As a result, places like James Cancer Hospital have started scheduling booster shot appointments for cancer and other immunocompromised patients.

Lucy McBride, an internist in Washington, D.C., said she's generally followed CDC and FDA guidelines regarding booster shots, but added that some of her patients don't neatly fit within the established booster shot criteria.

For example, McBride said she'd advise patients living with family members who are severely immunocompromised, or older patients who work in areas with high rates of coronavirus transmission, to get a booster shot.

Other providers have referred patients to pharmacies and other vaccine sites, many of which rely on patients' self-attestation of their health status. CVS Health and Walgreens have said they will provide booster shots to anyone who signs a form stating they meet CDC criteria for the shot—but neither chain requires verification of a patient's immunocompromised status.

Some doctors have said boosters should be given to patients only after immunity has waned and in efficient dosages, but that data isn't clear yet, the Journal reports.

Additionally, some doctors and health officials have said they don't believe patients should get booster shots until more vaccines are administered to the unvaccinated and given to developing nations with limited supply.

World Health Organization Director-General Tedros Adhanom Ghebreyesus said earlier this month that there isn't sufficient data to suggest booster shots are necessary for healthy patients and asked that wealthier nations wait to administer boosters until the end of this year.

But while some leaders advocate for a delay in administering the additional vaccine doses, many health officials acknowledge that the boosters will eventually be necessary. "Most likely we are going to all need boosters at some point, because that's just how vaccines work," Megan Ranney, a professor of emergency medicine at the Alpert School of Medicine at Brown University, said.

And until a universal booster recommendation is made, much of the decision-making continues to fall on doctors. "Because the messaging has been so confusing and because the data is still evolving, we're basically asking patients and pharmacies to make their own decisions," McBride said. "At the end of the day, it comes down to the person in front of me, and because the CDC can't possibly speak to every American, they have to draw these somewhat arbitrary lines in the sand." (Mauldin/Jamerson, Wall Street Journal, 9/19; Thomas, New York Times, 9/19; Whelan, Wall Street Journal, 9/20)