If you got a J&J shot initially, you should *definitely* get a booster.
And if it was us (and it was, for some of us), we would pick an mRNA booster. It’s not likely to produce worse protection, and it eliminates the very small risk of a serious adverse event linked to the J&J vaccine. Don’t worry too much about the fact that you have two doses instead of three after you’re boosted. It may not matter.
For those of us who got the 1-dose J&J vaccine, all the talk about 3rd vaccine doses can feel a little alienating. It’s confusing because our primary vaccine was actually only one dose–so what does that mean for our boosters? Will we ever end up with three doses?
Here’s what we know: studies in South Africa and the United States showed that J&J vaccine recipients who got a second J&J dose after either 2 or 6 months (that is, a booster) were very well-protected against the worst COVID-19 outcomes. Protection was similar to people who originally got one of the 2-dose mRNA vaccines followed by a booster. In October 2021, the FDA authorized J&J recipients to get a booster dose–of whichever vaccine type they choose–two months after their initial J&J dose. The data about J&J booster efficacy was pretty weak at that point, but nonetheless it suggested boosters could be important. Either way, J&J vaccine recipients end up with just two doses, not three.
Then, in December, CDC quietly dropped their recommendation for the J&J vaccine altogether. It’s still authorized for use, and you could still get it if you wanted, but CDC now recommends one of the mRNA vaccines, including for booster doses for those who originally got a J&J vaccine. This change wasn’t due to efficacy issues, but rather because of a small but growing number of cases of an extremely rare, serious adverse event involving blood clots. There have been 54 cases of thrombosis with thrombocytopenia syndrome (TTS) in the U.S., and 9 people have died. That’s about 1 death in 1.9 million doses given. Note: TTS occurs within a couple of days of getting the vaccine, so if you got J&J a while ago, you don’t need to worry about this at all.
Now, all of this was before omicron. More data out of South Africa came out in January indicating that people who got J&J and then were boosted with J&J were 85% less likely to be hospitalized compared to people who got J&J and were not boosted. They also found that, as with the initial vaccine dose, the efficacy actually goes up over time, at least for a little while. Protection was strongest 1-2 months after the booster. At the same time, at least one lab study showed much higher neutralizing antibodies in J&J recipients who mixed it up and got boosted with a single dose of an mRNA vaccine.
No matter which booster you go with, you end up with two doses total, not three. All boosters at this point are a single dose; there’s no two-dose option. For now, data suggest that just one booster shot offers excellent protection, no matter which combination you get. We will wait for signs that a 3rd shot is even better for people in this situation, but right now there aren’t any. It’s possible that the timing of doses is more important than the total number of doses. So don’t worry too much about the fact that you have two doses instead of three.
So what’s the (ahem) upshot? If you got a J&J shot initially, you should *definitely* get a booster. And if it was us (and it was, for some of us), we would pick an mRNA booster. It’s not likely to produce worse protection; it might offer better protection; and it eliminates that tiny risk of TTS.
Links:
YaleMedicine – You Got the J&J Vaccine: Should You Get the booster?
Reuters – J&J booster 85% effective against Omicron hospitalisation, South Africa says
