Many Americans can now get a second COVID-19 booster, but it’s hard to say who really needs another shot right now and who can wait.

The U.S. Food and Drug Administration authorizes additional Pfizer or Moderna vaccines for anyone 50 years of age or older, and some young adults with severely compromised immune systems. That’s an effort ahead of the next possible coronavirus surge.

With the low number of COVID-19 cases in the U.S., it’s easy to ignore calls for another dose of the vaccine — or those who haven’t been vaccinated or boosted to stay up-to-date, said Dr. Erica Johnson, an infectious disease expert at the American Council. Internal Medicine.

Her advice: If you’re indecisive, use this calm time to talk with your doctor about how protected you really are – and how much you need it.

Who is eligible for the second booster?

Anyone 50 years of age and older can get an additional dose at least four months after their last vaccination. Severely immunocompromised patients, such as organ transplant recipients, can be as young as 12 years old.

Adults can choose the Pfizer or Moderna vaccine as an additional shot, but Pfizer is the only option for children.

What about those who got JOHNSON & JOHNSON?

Adults who received a single dose of J&J’s vaccine are already eligible for any type of booster — the Centers for Disease Control and Prevention recommends that only some of them get another dose.

A second injection of Moderna or Pfizer is better than getting a second dose of J&J, a new study finds. Therefore, anyone who is now getting a second J&J shot is advised to opt for either Moderna or Pfizer’s dose.

But if they’ve already used one of these other boosters, the CDC says only those who meet the latest criteria (age or a weakened immune system) are eligible for the other.

What prompted this move?

The vaccine still provides strong protection against severe disease and death, but its effectiveness against mild infections wanes after a few months. The shots also don’t work against newer variants like super-contagious omicron mutants as they did in the early days of the pandemic.

That’s why everyone 12 and older, regardless of their health status, has been urged to get their first booster for the best chance of fending off omicron. Only about half of those who qualify have.

As the omicron siblings have led to a surge in infections in other countries, officials fear the U.S. is next, prompting efforts to provide additional protections for the most vulnerable.

What’s the evidence for another booster?

Many scientists say this is limited, leaving public health officials to use their best judgment.

During a U.S. omicron wave, two doses of Pfizer or Moderna plus a booster were 94 percent effective against death or needing a ventilator, according to a recent study by the U.S. Centers for Disease Control and Prevention. Among immunocompromised people, this protection was lowest — 74 percent, although most did not get the already recommended third dose.

Israel began offering second boosters for those 60 and older during omicron surge. Preliminary findings published online last week showed fewer deaths among people who opted for another booster dose than those who skipped the fourth dose.

The FDA decided to set the age limit at 50 instead of 60, because that’s when chronic diseases like heart disease or diabetes become more common, making people more vulnerable to severe COVID-19.

Who really needs a second booster?

The CDC says additional shots are an option — but those most likely to benefit are those most at risk of developing serious illness, including those 65 and older and those in their 50s with multiple health problems.

When should I get it?

Again, experts disagree, in part because it’s unclear how long any additional benefits will last.

“We’ll never be able to really pinpoint exactly when the next wave will come, or when someone might become infected,” said Johnson, who sees patients at Johns Hopkins Bayview Medical Center in Baltimore. “To be as prepared as possible, I think Everyone needs to know as much about their vaccine as possible.”

Now another dose may make sense for the elderly and immunocompromised, but “it’s less urgent in otherwise healthy people,” said E. John Wherry, an immunologist at the University of Pennsylvania.

At 50, Wherry said he was healthy enough to see if cases rose enough to prompt another booster, but he would prefer to wait until the fall. This is because a longer interval between vaccinations allows the immune response to mature and strengthen better.

The Associated Press Health and Science Division was supported by the Howard Hughes Medical Institute Division of Science Education. The Associated Press is solely responsible for all content.