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I just never got the latest COVID booster. Should I go for it? And when should I get it for maximum holiday protection when traveling and partying?

If you're among those who haven't rolled up a sleeve for the latest version of the vaccine — which rolled out in September — you've got plenty of company.

A December 2 report from the Centers for Disease Control and Prevention finds that in the U.S., for example, just under 20% of eligible people have gotten the updated vaccine, which has been updated to better match currently circulating variants of the virus.

"That uptake is nowhere near where it should be," says Dr. Robert Hopkins, medical director of the National Foundation for Infectious Diseases.

And who's eligible? According to the Centers for Disease Control and Protection, everyone 6 months and older.

You may be wondering: Do I really need it if I'm in good health?

Data shows that COVID vaccines are protective against severe disease and long COVID, reducing the risk of an emergency room or clinic visit — and the risk of death. Plus, "potentially preventing any COVID infection keeps you from being sick, getting long COVID and making someone sick who could really be at risk," says Jeffrey Townsend, a professor of evolutionary biology and head of a lab at the Yale School of Public Health that has been studying COVID throughout the pandemic.

But maybe you've just had COVID…And you're wondering. Isn't that giving me enough protection?

Just as protection from the COVID-19 vaccine decreases with time, so does immunity after an infection..

If you're ready to go for a jab, you might have a few questions. Like: Which of the three available vaccines to go for? There are mRNA vaccines from Pfizer and Moderna and a non-mRNA version from Novavax.

(mRNA vaccines use mRNA created in a laboratory to teach our cells how to make a protein — or even just a piece of a protein — that triggers an immune response inside our bodies. The Novavax vaccine is based on an older technology. "Between the two mRNA vaccines from Moderna and Pfizer, there is no reason to get one over the other," says Andrew Pekosz, vice chair of the Department of Molecular Microbiology & Immunology at the Johns Hopkins Bloomberg School of Public Health. "The [mRNA vaccines] target the same variant, are similarly effective and elicit similar side effects."

Pekosz adds that the Novavax protein-based vaccine will also "generate immune responses that recognize current variants," noting adding that people who have had a particularly adverse response to a previous mRNA vaccine might consider the Novavax vaccine as an alternative, as protein-based vaccines generally don't induce as strong side effects.

As for timing, if you'd like maximum protection for end-of-year travel and partying, keep in mind that it takes about two weeks for the vaccine to be fully effective. And while COVID isn't surging at the moment in the U.S. and other places, Dr. Hopkins says winter outbreaks are expected — a winter surge has always been part of COVID's timetable.

Meanwhile, if you've had a recent COVID infection you have a different vaccine timeline. Because you develop antibodies to the virus after a COVID infection, the CDC says people "may wait" three months after an infection to get the vaccine. That's because the immune response to the new dose will be strongest if your antibodies are waning.

There's a new study that looks at vaccine timing. The study is geared toward a future time when COVID has a clear season where it regularly peaks (as flu does), but it does contain relevant info on so-called "breakthrough" infections — when you catch COVID soon after being vaccinated.

In the study, published in Clinical Infectious Diseases, study author Jeffrey Townsend and his team recommend a timetable: for someone who got a booster in September, then caught COVID between October and April. The optimal time for the next dose is the following mid-to-late September. For breakthrough infections between mid-May and early September, the wait time before the next booster falls to six months because of the likelihood of a winter outbreak.

Townsend says the study's recommendations are different than the CDC's because the agency looked at when antibodies begin to fall, and the study looked at when antibodies fall to the level where you'd be vulnerable to reinfection. But the study does not offer official guidance so a conversation with your doctor might be in order.

"Many of my colleagues have discussed that timing of vaccination relative to infection is something we need to be taking into account more," says Dr. Abraar Karan, an infectious disease researcher at Stanford Medical School. He advises people to test if they have COVID symptoms in part so they can fine tune their vaccine schedule.

"Doctors have to take into consideration what's unique to the patient in front of them," says Amesh Adalja, senior scholar at the Center for Health Security at Johns Hopkins Bloomberg School of Public Health For example, people who are immunocompromised may be advised to boost more frequently since their antibodies can wane faster. And people who are 65 and older have been advised by the CDC to get a second dose of the new booster six months after the first.

Of course, even having a debate over whether to get an updated vaccine is a rich world problem. Rebecca Weintraub, an associate professor of global health and social medicine at Harvard Medical School says that while most countries haven't reported their uptake of booster doses, the educated guess is that boosters are not widely available in low- or middle-income countries. For one thing, COVAX, the program that deployed vaccines in lower- and middle-income countries, closed up shop at the end of 2023. "In many countries," says Weintraub, the COVID vaccine shifted into the regular immunization program with some countries choosing to prioritize vaccines for other conditions." Weintraub says that when COVAX closed, only 57% of eligible folks had received two doses in low- and middle-income countries, compared to a global average of 67%.

And even in the U.S. there's no guarantee that the supply of boosters or messaging to promote them will continue. Jennifer Kates, senior vice president and director of the Global Health & HIV Policy Program at health research group KFF, says the next administration "has significant authority to affect both the availability of COVID vaccines and messaging about their importance, authority that will undoubtedly influence individual behavior and state and local decisions."

Kates says the FDA Commissioner has the authority to approve and authorize new formulations of COVID vaccines and the CDC Director has the authority to set recommendations for the public. "Messaging around vaccines is an important [U.S. Department of Health and Human Services] function, and the frequency, cadence, content, and channels of such messaging will set the scene for how vaccines are received by the public."

And while doctors' offices often no longer stock COVID vaccines, Weintraub says, many pharmacies do. And you can often schedule an appointment on line. If you are insured, your insurance will cover the cost so long as the pharmacy or doctor is in network. No insurance? Call your local health department to ask about free or low-cost options. (Without insurance the cost is over $200 — the federal government no longer covers the cost for everyone as it did at the height of the pandemic.)

Fran Kritz is a health policy reporter based in Washington, D.C., and a regular contributor to NPR. She also reports for the Washington Post and Verywell Health. Find her on Twitter: @fkritz

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