Thread by @michaelzlin

Not surprised that FDA rejected the inactivated vaccine Covaxin (produced by Bharat, marketed by Ocugen) for 2-18yo. Bharat-Ocugen presented data that their vaccine produced higher antibody levels than adults, and applied for EUA based on that:
ir.ocugen.com/news-releases/…

The data were only collected in late 2021. Impressive Ocugen was able to complete a EUA application so quickly, but they apparently did so without feedback from FDA as to the sufficiency of the data (or ignored such feedback). Data are below
medrxiv.org/content/10.110…

The problem is that among 2-5yo, whom we don't have a vaccine for, we don't know the relationship between antibody titers and VE in terms of protection from infection or symptomatic cases, at least not publicly. The only people measuring those outcomes are Pfizer and Moderna.

And as we know, Pfizer's vaccine for 2-5yo has insufficient VE for approval after 2 doses (presumably VE <50), so we don't have data on what Ab levels correlate with VE >50.

The problem isn't that antibodies in kids would act differently than in adults (likely they would do similar things at similar concentrations), but that kids might have a higher baseline for clearance without vaccination to begin with.

The effect of having those antibodies ahead of time may be marginal on top of what the children's bodies are doing already. It won't hurt, but FDA requires knowledge of what the VE is, not just anything >0%.

I'm guessing (someone can check) that Pfizer chose their 3mg dose because the levels of elicited Abs were similar to vaxxed adults. Bharat says children's Abs are 1.6x of adults. But that would still not be as high as Pfizer or Moderna in adults which are 3-6x higher than Covaxin

Actually I checked myself. You can see Pfizer's 3ug dose chosen for 2-5yo produced more nAbs than the approved dose for 16-25yo, which we know had VE>50% pre-Omicron. But this 3ug was not sufficient in kids (although not clear if FDA is using Omicron cases now to judge)

Regardless, if Pfizer's vax for 2-5yo makes similar nAbs as their approved vax for 16-25yo, but has insufficient VE, then Covaxin making even fewer nAbs is not likely to have sufficient VE either.

Now you'd think Ocugen could so such calculations themselves. I don't know if they had data to the contrary or decided to submit an application even if they expected rejection.