Which booster to get (mixing vaccine brands)

It sounds like the FDA has approved mixing and matching shots, and I’ve also heard some preliminary evidence that having mixed vaccines work better than all-of-one-type. I got my Pfizer rounds back in April. Should I do Moderna when the time comes for me for the booster? What’s the real state of the evidence here?

ETA: hey, I can edit my own title! (I must have missed the memo on that…)

The wording in the articles is confusing. There was a tiny NIH study that released interim findings that “a different vaccine, used as a booster, raises your antibody levels”, or something like that.

The same vaccine, used as a booster, ALSO raises your antibody levels.

I’ve spent way more time poring over the findings of that study (which has 50 people in each of the 9 combinations of primary series and booster, and they only published complete data for days 1 and 15, that is, before boosting and two weeks later) and i would summarize the results as:

Boosters work
It’s safe to mix and match
In general, the strongest immune response is generated by Moderna, Pfizer is a notch behind, and J&J appears to be worst, at least by what this study has measured to date.

The other really interesting finding is that J&J boosted by J&J appears to be by far the worst combination you might pick. In fact, it looks comparable to unboosted Pfizer and a notch below unboosted Moderna.

But: this study only looked at antibody levels. It didn’t look at real world outcomes, nor even at cellular immune responses. (B and T cells.) And it’s a very short time window.

Still, I’m pointing all my friends who got J&J at this. I think they’ll likely so better if they get a different one as a booster.

(I’ll try to point to it here, but not now. The study was released as a PDF and it’s hard to link to it from my phone.)

Is that the only study (the tiny NIH one) you’re aware of that looked at different permutations of vaccine types?

There was a large Spanish study of mixing AZ and Pfizer fit the first two doses. And Canada has been encouraging people to mix and match their first two doses. There may be enough data to learn something from that natural experiment, although of course they aren’t drawing blood from matched participants or anything.

Also, I’ve just enrolled in a study of J&J as a booster to Pfizer, but it won’t have data for quite a while, yet, given that i enrolled today.

I think we did a mix & match on about 2 million AZ 1st dose recipients in Canada, so I am the proud owner of 1 AstraZeneca and 1 Pfizer. My wife is Pfiderna.

If I were a J&J person, I would probably choose moderna as my booster. But I’m a pfizer girl, and it wasn’t available when I got my booster, so I shall remain pfizer.

Breaking news:

CDC signs off on Moderna and Johnson & Johnson boosters and says people can get a shot different from their original one

Yesterday [10/20] at 5:34 p.m. EDT | Updated today [10/21] at 8:30 p.m. EDT

Whatever original shot(s) you got, you can now get any of the boosters. This does not imply which combinations they recommend, apparently they will work out those details Real Soon Now. The boosters are approved under EUA rules for specific age groups, or vulnerability group, not for just anyone and everyone (yet).

Thanks for that link! I’m a J&J receipient and I’ll be getting a Moderna booster next Monday (I have a bunch of IRL stuff to do before then.)

It’s unlikely to cause a problem, and if there’s something about either vaccine (pfizer/moderna) that has some sort of unique beneficial effect, then combining those effects would probably give you the greatest protection. That seems logical, the data isn’t really there to make a call.

That said, it seems that moderna performs better against Delta (whereas the data seemed to suggest that Pfizer did better against the original variant), so right now the moderna seems to be best. Since you’ve taken pfizer, both factors (mixing may have a benefit, moderna is currently better) point you towards getting the moderna booster.

I’d like to see a coffeeshop-style frequent-user punch card for anyone who plans to continent-hop collecting all the possible options. :wink:

I already got my third shot of Pfizer about two weeks ago, so I guess that’s what I’m rolling with at least until they decide it’s time for a fourth dose.


I also got my third Pfizer shot about a week ago. In another 6 months or so, if they recommend yet another booster, I think I would consider getting the Moderna.

My adult son, on the other hand, got the Moderna for his first two shots. He may be eligible for a booster in a few weeks. However, since my son got his original vaccine, there have been reports of heart inflammation complications from the Moderna vaccine, especially in young men. It’s fairly rare, but carries a risk several times higher than the Pfizer vaccine. In fact, several countries in Europe no longer recommend the Moderna vaccine for men under the age of 30. So with mixing and matching now being allowed, I’m wondering if he should get a Pfizer booster instead. Any thoughts on this?

Yeah, I think that’s what I’m leaning towards, though I don’t hit my six months until next week, and if I’m eligible at all, it’ll be under the ‘job exposure’ option.

I also realize I didn’t specify, but @robby brought it up: I’m male and in my mid-40s. As far as I know, I’m in a pretty safe demographic for any/all of the shots.

My adult son asked me the same question last night.

My best guess is that it doesn’t matter very much. But i told him any booster should give him enough immunity.

As I noted in the J&J thread just now, I got a Moderna 0.25mL booster on top of my previous J&J. I hadn’t really paid attention to dosage in the past, but I’m a little curious about how they decided to set the volume at half the previous dosage.