How to choose which booster shot is right for you, between Pfizer and Moderna

Many are wondering which is the best booster shot to get now that free shots are being offered to all adults.

All of the authorized COVID-19 vaccines do a good job, and you can boost with whichever vaccine you want. The three have been deemed safe.
There are some small differences in the vaccines that could be a factor in your decision making, especially for older adults who may prefer Moderna's.
Moderna's vaccine tends to prompt slightly stronger immunity, and it also seems to elicit slightly higher levels of antibody than the other two vaccines. It doesn't mean it's a better vaccine in the long run, but it does seem to give Pfizer at least a little bit more protection in the immediate term.

Dr. William Moss, who directs the International Vaccine Access Center at the University of Baltimore, said that he doesn't think there's a strong argument for picking one vaccine over the other. I would say that either is more convenient to get.
Most US adults have stuck with their original brand.

All adults are advised to get a booster shot six months after their initial series, except for those who've gotten Johnson & Johnson's single shot vaccine, who have been advised to get a booster at any time past two months after their initial shot.
Federal data shows that most people who get a booster shot stick with their original brand.

Moderna boost seems to be a preference for Johnson & Johnson takers. J&J users might benefit from this "heterologous" boosting strategy if they switched vaccine platforms.
J&J vaccinees seem to have a preference for Moderna boost, even though most people who have gotten mRNA boosters have stuck with their original brand. Data from December 1, 2011.

The Centers for Disease Control and Prevention.

Moderna's shot is larger than Pfizer's.

Moderna's booster is a half-dose of the original vaccine. Many vaccines have half-dose boosters, and they work well.

Pfizer's booster is the same size as the first two shots and has 30 micrograms of mRNA in it.
Pfizer's vaccine gives a strong boost to the immune system, meaning that people who get boosted with it will benefit from increased protection against infections for at least a few months afterwards. Scientists are still figuring out how long the extra protection lasts and how good it is.

Moderna's vaccine may be more powerful than others.

Moderna's vaccine performs slightly better at keeping older people out of the hospital, according to some emerging clinical data.

Moderna's vaccine was associated with a 21% lower risk of confirmed infections and a 41% lower risk of hospitalization compared to Pfizer's vaccine, according to a Veterans Affairs study published on December 1. Moderna's vaccine elicited the most robust antibody responses afterboost, while Pfizer's vaccine was marginally lower, and Johnson & Johnson took third place.
It might be a better booster for elderly adults, who are more vulnerable to severe outcomes, and need more frequent and potent boosters of all kinds.

The side effects are different.

The company recently made a presentation to the Centers for Disease Control and Prevention about the benefits of getting a third shot of Moderna's vaccine. The same is true for both companies.
Moderna's vaccine tends to be more reactogenic than Pfizer's, so people who switch to it for their booster may notice their Moderna side effects are a little higher. The most common complaint after a booster shot is some pain at the injection site. There are also headaches, fatigue, and muscle aches.

People in the company's clinical trial were more likely to complain about their armpit swelling after their booster shot. Pfizer trial recipients reported a bit more swelling after their boost.

People who got Johnson & Johnson's shot, and stuck with the same brand for boosters, tend to report similar side effects for a second shot compared to their first.
The adverse effects of booster shots are usually temporary and mild to moderate.
It's all the same, according to many experts.

Over the next several months and years, it will be clear what the best COVID-19 vaccine strategy is. In the meantime, infectious disease experts don't think too much. People with just one J&J or two Moderna shots are more protected against the virus than people with more than one booster shot.
Dr. Anthony Fauci, the nation's top infectious diseases expert, recently told Insider to not make it complicated. The effect of boost is very positive to preventing people from getting infections.

It's generally agreed that it's reasonable for all adults to get boosted with whichever shot they choose, ahead of the holiday gathering season.