Can I boost with an mRNA vaccine if I got Sinovac or Sinopharm originally?


A: Yes, you can. If you got Sinovac or Sinopharm originally, it won’t hurt to boost with an mRNA vaccine–and it might help.

No one really knows what the BEST combination is at this point, but overall protection is higher for those who do opt for a different brand booster shot. And most important, there have been no safety issues among those who opt for a different brand booster.

If you got the Sinovac or Sinopharm vaccine when it became available, you’re probably wondering: which booster should I get? Is it safe to get a Pfizer or Moderna booster if I got Sinovac originally? Is it as effective (or perhaps even more effective) than sticking with the original vaccine brand?

“Mix-and-match” refers to whenever we get one vaccine type for the primary series and then another type for the booster. There are a lot of COVID-19 vaccines out there at this point, but all of them do the same thing: they train our immune system to recognize a threat by showing something similar to our immune cells. Some vaccines (like Sinovac and Sinopharm) contain copies of the whole virus that have been killed. Others (like the vaccines from Pfizer, Moderna, J&J, and AstraZeneca) just show our immune cells a key part of the virus.

Mixing two different vaccines can produce better immunity than using just one because the immune cells become familiar with slightly different versions of the threat, and can therefore recognize it even better. Mixing one dose of AstraZeneca and one of the mRNA vaccines (Pfizer or Moderna) can offer better protection than AstraZeneca alone. We also know that after two doses of Pfizer, a Moderna booster can produce better protection; and after two doses of Moderna, a Pfizer booster can produce better protection.

Not much is known at this point about the effectiveness of getting one of the mRNA shots if you had Sinovac or Sinopharm first. But it’s unlikely to be WORSE than boosting with the same vaccine you had originally. And some preliminary results out of Chile show that boosting Sinovac with Pfizer was safe and more effective, compared to a booster of Sinovac.

In Singapore, people who originally got Sinopharm are being steered toward either Pfizer or Moderna as a third dose, though they can also get a third dose of Sinopharm if they choose. In a few months, we’ll get a better picture of any “boost” in effectiveness from studies coming out of this policy.

Most important, no safety issues have been raised for any of the COVID-19 vaccine combinations so far.

Useful summary here

And a couple of past DP posts on mix-and-match:

If I got the Johnson & Johnson vaccine, can I get the Pfizer or Moderna vaccine if a booster shot is needed?


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