Thread by @profshanecrotty

SIX successful COVID-19 vaccines! SIX! Three just in the past week! Extraordinary. The newest one is the Russian (Rus) adenoviral (Ad) vector COVID vaccine. The clinical trial data look really good at face value. 🧵

doi.org/10.1016/S0140-…

92% efficacy overall, and 92% efficacy in people over 60 years old.

I will let clinical trial design experts weigh in on trial design features. I will comment on the basic outcomes and the immune responses.

The protection results are in line with the immunogenicity data, in comparison to several other vaccine trials.

In the earlier Rus clinical trial, the vaccine elicited strong neutralizing antibodies after 2 doses. Those levels appear to be in line with the 2-dose RNA vaccines
doi.org/10.1016/S0140-…

The Rus protection results appear to be better than a single dose of the J&J vaccine (for which full numbers are not public yet), but the Rus vaccine was 2-dose.

The Rus vaccine saw 8x more neutralizing antibodies after the 2nd shot. J&J got 4x more neutralizing antibodies after 2-dose compared to 1-dose.

So, it is reasonable to expect that the ongoing J&J 2-dose COVID vaccine clinical trial will do quite well.

doi.org/10.1056/nejmoa…

Of note, the Rus vaccine had only sporadic neutralizing antibodies after a single immunization with Ad26-S (11/18 positive at all). In contrast, the J&J vaccine (which uses a P-P stabilized S) had much more consistent neutralizing antibody responses after a single dose (91%-99%).

CD4 and CD8 T cell data followed the same trend. 1-dose J&J appeared to be more consistent at CD4 and CD8 T cell responses than 1-dose Rus.

The adenoviral vectors elicit a good CD4 and CD8 T cell response in both cases for the condition used in the efficacy trial (1-dose J&J. 2-dose Rus), and those T cells may be important for protecting against variants.

Ad26 vector vaccine approaches have been extensively developed by Dan Barouch and colleagues over the past 10+ years, and that approach is used in both the J&J and Russian vaccines.

Bottom line: more good vaccine news (SIX vaccines!), with protection against COVID generally consistent with the immune response data.