Thread by @nataliexdean

The news about Pfizer's adolescent trial is excellent. As some debate whether we have enough data to reliably estimate vaccine efficacy in this subgroup, some important context is that efficacy was not even the primary outcome of the trial. 1/4 statnews.com/2021/03/31/pfi…

The 12-15 subgroup was comparatively small (an extension of the existing trial), and the focus was to measure safety and immunogenicity, although efficacy data was also collected. Though we don't have full details, the trial was unlikely powered for efficacy. 2/4

When we think about bridging a known efficacious vaccine to a new (here, younger) population, the bar for evidence is lower. Clearly we need high quality safety data. For immune response data, we see even higher antibody responses in adolescents than adults. 3/4

But these data are coupled with our existing understanding that the vaccine works well in adults 16+. So the strong 18 vs. 0 case split serves to confirm/replicate an existing result, and does not have to stand alone as a new result. 4/4

Addendum: Here is the incredibly complicated clinical trials listing for the Phase 1/2/3 trial. Fingers crossed I am communicating this all accurately.
clinicaltrials.gov/ct2/show/NCT04…

As an example that is easier to see, here is the clinical trials listing for Moderna's Teen Cove study. The primary outcomes are related to safety and immunogenicity. Efficacy is defined as a secondary outcome.
clinicaltrials.gov/ct2/show/NCT04…