Thread by @DrEricDing

New 50% efficacy study of Brazil-predominant vaccine CoronaVac (by Sinovac) in Manaus 🇧🇷 among healthcare workers when #P1 ~75% dominant. Not a trial, but the study found a 1st dose >=14-days efficacy of 50% on symptomatic #COVID19, ~32% if +asymptomatic. medrxiv.org/content/10.110…

2) Sorry I meant ~35% if asymptomatic included with the symptomatics. But it’s not significant. Wide CIs.

3) Sinovac’s CoronaVac efficacy is all over the board. It was 50% for 2 dose efficacy in a Brazil trial, but it had 91% efficacy in early Turkey trial, and 65% in an Indonesia trial.

nature.com/articles/d4158…

4) Then Turkey revised down its earlier 91% symptomatic efficacy to 83.5% in March.

But they note CoronaVac “prevented hospitalisation and severe illness in 100% of cases, saying the six people who were hospitalised were all in the placebo group”.
google.com/amp/s/mobile.r…

5) another lab study “found that plasma from eight people vaccinated five months ago with CoronaVac “failed to efficiently neutralize” P.1. The study didn’t show if CoronaVac can still stop people getting sick from the variant”

google.com/amp/s/www.wsj.…

6) However the Brazil researchers at Butantan Institute “stressed that the vaccine is 78% effective in preventing mild cases that needed treatment and 100% effective in staving off moderate to serious cases.”

google.com/amp/s/www.bbc.…

7) it’s really hard to pin down the exact P1 efficacy since trials didn’t sequence the cases for which variant. We just know in Manaus that it was 75% roughly during the study.

Meantime here is some data on the mRNA vaccines and #P1 neutralization (lab study, so not efficacy)

https://twitter.com/DrEricDing/status/1371209487491735553

8) 54% overall efficacy for SinoVac for 2 doses.

“However, protection with only one dose is estimated to be 3%; for those with two doses with less than 14 days is 27.7%; and 56.5% effectiveness for those who have the second dose more than 14 days ago.”

emol.com/noticias/Nacio…