So the @Novavax results showing 90% vs. 49% efficacy make the results of the @JNJNews results even more exciting. JNJ is evaluating their Ad26 vaccine in S Africa as well. Divergent results *may* give a clue to the role of CD8+ immunity in vaccine elicited protection. Nerd

Novavax, JNJ, Pfizer and Moderna's vaccine all use the exact same antigen sequence (a full length prefusion stabilized spike protein). But Novavax's vaccine is a subunit vaccine, meaning that it the vaccine is just the antigen bound to nanoparticles w/ an adjuvant.

This is distinct from JNJ, Pfizer and Moderna vaccines, which use DNA vectors or mRNA to teach human cells to "make" (translate) the antigen themselves. This is critical for a inducing a specific type of T-cell immunity controlled by CD8+ T cells.

This is due to something known as MHC class restriction. But tl;dr, all of the vaccines can induce an antibody response (in B cells), and a type of T-cell response (in CD4+ T-cells). But only mRNA vaccine or DNA vaccines can induce a CD8+ T-cell response.