Thread by @michaelzlin

FDA has granted regular approval to the Novavax vaccine. What does this mean? A lot of things, all good.

1- It proves Novavax has met efficacy and safety criteria to merit approval outside of the emergency use situation.

Novavax is safer than the RNA vaccines, but ironically the RNA vaccines received full approval earlier than Novavax. That meant Novavax was the only COVID vaccine which vaccine skeptics could incorrectly claim was not safe enough to receive regular approval.

2- Novavax will get to participate in annual booster updates on the same terms as the RNA vaccines. This year's advisory committee for booster strain selection has already been scheduled.

3- All health insurers should now cover Novavax.

4- Novavax provides an option for those reluctant to take RNA vaccines, or who simply want milder side effects. This should increase vaccination rates compared to the situation of no Novavax, which is good for everyone

5- In theory Novavax can now be given off-label to children under 12 🤔

There are postmarketing requirements. They are all about figuring out rates of myocarditis. We have good data on rates with RNA vaccines because 650M (!) RNA doses were given 2020-2024, whereas only 0.08M Novavax doses were given. That's 8000x fewer!

ourworldindata.org/grapher/covid-…

As far as I can tell, there were 0 myocarditis cases reported in VAERS for Novavax whereas there were 1991 for RNA vaccines in 2020-2022 alone.

With 8000x fewer Novavax doses, you'd actually expect zero myocarditis reports even if the risk were the same

jamanetwork.com/journals/jama/…

Here are the postmarketing requirements and a link to the FDA letter. Novavax is obliged to track a larger pool of patients to assess myocarditis rates, in various subpopulations

fda.gov/media/186545/d…

When Makary said new studies were needed because the current Novavax product is not the same as the earlier one for which data was provided, perhaps he meant that myocarditis rates need to be remeasured since the production method has changed. Fair enough.

https://x.com/michaelzlin/status/1916261587435803058

Finally, the approval also eases the way for Novavax to test their combination COVID19 and flu vaccine, and validates their Matrix-M adjuvant and manufacturing processes in general. These were the reasons Sanofi took a stake in Novavax.

Now the FDA added some odd condition that the vaccine is for those with conditions that increase risk of COVID complications. Given its better safety, it seems backward to put this on Novavax and not the RNA vaccines. But I'd hope you'd be allowed to self declare.

And you wonder if that restriction is going to come later for the RNA vaccines

Interestingly, when FDA granted full approval to the Pfizer vaccine, there were requirements for 13 postmarketing studies. So Novavax's requirements here are relatively light

The @statnews article suggests that future vaccine recommendations will also be limited to older adults and those at higher risk, so it could be the restriction on Novavax is just the first manifestation of a broader policy in this direction.

statnews.com/2025/05/17/fda…

@statnews Finally I forgot to say that full approval gives Novavax the ability to advertise/educate. I doubt they will do this for the lay public (too expensive and risks backlash) but doctors and pharmacists could use some education. Many don't even know there is a non-RNA COVID vaccine.