It’s OK to mix and match COVID-19 booster shoots. Which one should I get?

Topping up your protection against severe COVID-19 while avoiding the risk of rare vaccine side effects should not be rocket science.

But ask federal regulators The experts who advised them to authorize additional shots There is no single formula that can guide Americans in making decisions about booster shots.

Whether you should get a booster shot or which one you should will depend on your medical history, who you are and what vaccines you received first. Your choice could also be affected by the people you live with and the work you do.

And then there’s the deeply personal matter of how much risk — of COVID-19 or of vaccine side effects — you’re willing to accept.

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Even if a vaccine’s protection has slipped with time, many fully vaccinated young people, or those who’ve had an infection before or after being vaccinated, can reasonably decide that their likelihood of becoming very sick remains low.

The experts who advised the Centers for Disease Control and Prevention this week made clear they were not recommending boosters for all; they were recommending that millions of people who are fully vaccinated have access to a booster shot if they want one. A new government study has given rise to more options and more complexity in the matter of boosters. The results are preliminary and participants are still being followed. But after at least 12 weeks of follow-up, researchers haven’t detected any ill effects in people who were first inoculated with one COVID-19 vaccine and then got a booster shot of another. These reassuring results led Dr. Rochelle Walensky, the CDC director to give patients the option of choosing between two vaccines.

“Some people might prefer the type of vaccine they received originally, while others may prefer a different booster,” the agency stated in new guidance released late Thursday. “CDC’s recommendations now allow for this type of mix and match dosing for booster shots.”

Now, in addition to asking yourself whether you in fact need a booster, there’s the question of whether you should seek out a shot that’s different from the one you got the first time around. These are some things to keep in mind when making a decision.

Maximizing your boost

If you want to increase your immunity, the data are still not available.

The new study includes three groups of 150 fully immunized people — one that got the Pfizer-BioNTech vaccine, one that got the Moderna vaccine, and one that got the Johnson & Johnson shot. Researchers took each group and further divided it into three arms, with 50 people in each. Participants in each arm received the same product as they had previously received. The second and third arms of each group were boosted with the appropriate vaccine.

It’s an innovative and clever design. However, scientists are unable to draw meaningful comparisons between the groups because not enough people have been followed for long enough.

Initial efforts to measure coronavirus-fighting antibodies’ jumps showed that mixing was not necessarily worse than matching and sometimes even better.

With regard to the Johnson & Johnson vaccine in particular, the data suggest that those who got an initial J&J shot saw their antibody levels rise a bit more after 15 days if they were boosted with the Pfizer-BioNTech or Moderna vaccine than if they got a second dose of J&J. The increase in antibodies after either the Pfizer-BioNTech or Moderna boosters was roughly the same.

Safety considerations are the best way to determine who should mix and match.

Women considering a J&J booster

Through Oct. 13, vaccine safety monitors have detected 47 cases of a rare blood clotting disorder in people who got the single-dose J&J vaccine.

That’s a tiny fraction of 15.3 million doses of J&J vaccine administered. But the disorder — called thrombosis with thrombocytopenia syndrome, or TTS — is life-threatening. The condition causes runaway clotting, which is extremely difficult to treat. Five people died from it.

Three-quarters of J&J vaccine recipients who developed TTS were women ages 18-49. Four out of five people who died were female.

Tests that could predict someone’s likelihood of developing TTS aren’t available. So women under 50 who want more protection might consider seeking out the Moderna or Pfizer-BioNTech vaccine for their booster shot.

Young men who got a shot of Moderna or Pfizer-BioNTech

For every million young men between 18 and 24 who got a second dose of one of the mRNA vaccines, safety monitors detected somewhere between 37 and 39 cases of myocarditis or pericarditis — essentially an inflammation of the heart muscle or its surrounding tissue.

The rate was highest among men under 21, but it was seen with decreasing frequency in men up to 29. It was also seen in women but less often. It was slightly higher among young men who had received the Moderna vaccine as opposed to those who received Pfizer BioNTech.

The conditions became more frequent after the second dose. Experts fear that a third dose could increase the risk.

Myocarditis and pericarditis are pretty rare side effects, and in more than three-quarters of cases, their symptoms — tightness, squeezing or pain in the chest — went away with time and over-the-counter drugs. Heart irregularities should be considered seriously. No one knows whether inflammation can have long-lasting effects.

Cardiologists recommend that you stop doing strenuous exercise for at least three to six months following a diagnosis. A young male athlete who has had one of the mRNA vaccinations might want to get the J&J booster or switch from Moderna to Pfizer BioNTech if he feels he needs another shot.

Those with a history of Guillain-Barre syndrome

Guillain-Barre syndrome, or GBS, is a reaction to infection or vaccine in which the immune system attacks the nerves, sometimes causing paralysis that can last months.

The FDA’s adverse event monitoring system has picked up at least 130 reports of people across the age spectrum developing GBS after getting the J&J vaccine, but no rise among those who got mRNA vaccines. This week, the British government added a warning about rare cases of GBS following use of the COVID-19 vaccine made by AstraZeneca, which is not authorized for use in the U.S. but is similar in design to the J&J vaccine. Anyone with a family history of GBS should consider switching to one the mRNA vaccines to boost their immunity.

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