Since last December when COVID-19 vaccines first became available in the U.S., there haven't been a lot of choices. People got whatever vaccine was being offered at the local drugstore or vaccination clinic.
But within a few days, booster doses are expected to become widely available and everyone eligible will be able to choose their preferred vaccine: Pfizer-BioNTech, Moderna or Johnson & Johnson. The government will be making booster doses available for free.
And mixing and matching vaccines could be available by this weekend after the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices on Thursday unanimously voted to allow them.
Although there's limited data available, here's what studies and experts suggest is the best course of action for deciding who should get a booster and which one to get.
Who does or doesn't need a COVID booster now?
Studies in the U.S. suggest that the COVID-19 vaccines are still doing a terrific job of protecting against severe infection and death.
For the week ending Aug. 28, the unvaccinated were 18 times more likely to be hospitalized than those who were vaccinated, according to data presented by Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, at a Wednesday White House briefing.
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But nothing is perfect and there are categories of people who would likely benefit from a booster shot.
People who are immunocompromised – perhaps because they have received an organ transplant, are taking chemotherapy or are on immunosuppressive medication – are the first group that should consider getting a booster dose.
Experts warn that they should still be cautious, though, because not everyone who is immunocompromised will mount a response even to a third dose. They should continue to mask up in public and encourage everyone around them to get vaccinated to provide a "ring" of protection around them.
So far, about 6% of Americans have gotten a booster dose. About 9.5 million have received a Pfizer-BioNTech booster, about 1 million have received a Moderna booster and about 11,000 have gotten a J&J booster.
People will still continue to be considered "fully vaccinated" if they received two doses of Pfizer-BioNTech or Moderna or a single dose of J&J. The CDC does recommend people get their booster dose in the opposite arm from the previous doses, if possible.
Who else can get a booster besides the immunocompromised?
The Food and Drug Administration has authorized booster doses for the following groups of people, and the CDC is likely to do so in the next day or two. These boosters will be available for people who received the Pfizer-BioNTech or Moderna vaccines, six months after their initial doses.
People who are over 65: The immune system gets weaker with age. Death rates from COVID-19 are much higher among those over 65 than those who are younger. In Israel, people over 60 got a significant benefit from a booster shot, with infection rates – which were rising dramatically nationwide – turning downward in this age group about three weeks after booster shots began.
Adults who are under 65 but live in long-term care settings or have medical problems, such as diabetes or heart or lung disease may also benefit from a booster. COVID-19 seems to hit medically vulnerable people harder, including those who've had a stroke, Down syndrome, mental illness or a very high body mass index.
Adults under 65 whose jobs put them at increased risk of exposure to COVID-19, including healthcare workers and grocery store employees. These people are not more vulnerable to serious disease but they come into regular contact with many others and their absence from work could cause problems.
Anyone who originally got the Johnson & Johnson shot is eligible for a booster at least two months after their initial vaccine.
What do we know about 'mixing and matching' COVID-19 vaccines?
There’s only one small study, from the National Institutes of Health, comparing booster doses of one vaccine versus another – so while it can offer hints, the data is far from conclusive.
The study, while well conducted, has only been following people for about a month, so it can’t yet provide any insights into how long each booster might offer protection.
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There was some thought initially that it might be more protective to “mix and match,” because some of the vaccines work differently. But there’s no evidence that it’s better to get a different type of vaccine after first getting either the Pfizer-BioNTech or Moderna shots, which both rely on mRNA technology.
People may also want to switch brands if they had, for instance, a bad reaction to their initial vaccination.
I got Moderna for my first two shots. Which one should I get next?
Early data suggests that Moderna’s protection is stronger and more durable than the other vaccines and works well as a booster.
The Moderna regimen also provides a high dose of vaccine, so for boosters, the company is cutting the dose in half. Everyone who gets a Moderna booster will get a 50-microgram dose, as compared with the 100-microgram dose provided for the initial round of shots.
Data is extremely limited on the long-term effectiveness of this 50-microgram dose. It’s not clear if the benefits seen with Moderna’s vaccine are from its initial high dose or the power of the vaccine itself.
If you got Moderna originally, current data suggests there’s no reason to switch vaccines, but also no harm in getting Pfizer-BioNTech next.
I got the Pfizer-BioNTech shots the first time. Which one should I get next?
The same study found that following up Pfizer-BioNTech shots with another dose of the same vaccine was also strongly protective.
It’s possible that there might be a small benefit to switching to Moderna for a booster dose, but that’s based on very little data and it’s not clear whether the benefit seen on a lab test will be significant enough to show up in the real world.
I got the J& J single-dose vaccine. Which one should I get for my second dose?
The CDC advisory committee unanimously recommended that people get a second dose after a single J&J shot, aligning with studies that also support a follow-up dose.
The same small NIH study suggested that people will get a bigger boost by getting a second dose of an mRNA vaccine – either Moderna or Pfizer-BioNTech – rather than a second J&J shot.
Several members of the CDC committee said Thursday they felt strongly that people who got J&J for their first shot should switch for a booster, because of the risks of the vaccine and the lower protection it provides.
Are COVID booster doses safe?
Yes, all indications are that it’s safe to get a supplemental dose of COVID-19 vaccine.
All the company-funded studies have been too small to show rare reactions to the vaccine. Data from Israel, where booster doses of the Pfizer-BioNTech vaccine have been provided to millions of people show booster doses are at least as safe as the first round of shots, with perhaps fewer side effects.
Contact Karen Weintraub at firstname.lastname@example.org.
Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.
This article originally appeared on USA TODAY: COVID booster shot Q&A: Can you mix and match? Who needs one? Safe?