Thread by @hildabast

Preprint of results from the Novavax phase 2 trial in South Africa with efficacy outcomes, with 4,387 participants. Sequencing done for most of the people with Covid-19: 93% were infected with B.1.351 ("SA" variant). ...1/n medrxiv.org/content/10.110…

...Small trial, so a lot of uncertainty in efficacy results.

Vaccine efficacy rates:

Overall (not previously infected with SARS-CoV-2): 49.4% (CI 6-73)
HIV- : 60.1% (CI 20-80)*
Against B.1.351 variant: 51.0% (CI 0.6-76)

* 6% of people in the trial living with HIV

...2/n

...About 30% of people tested positive for previous SARS-CoV-2 infection, & their risk of getting sick with Covid-19 was the similar to people who'd never been infected before. Placebo group: 5.3% vs 5.2%. Previous protection didn't protect against the variant ...3/n

...The trial participants were predominantly young & black: only 4% were 65 or older; 95% were Black-African. Obesity rate: 20% ...4/n

...This is a vaccine that had a high efficacy rate in the larger UK trial (89% overall, 96% against original strain). It's a protein subunit vaccine - so a fairly traditional vaccine type ...5/n

...Adverse event (AE) data for the first week after injections from the early part of the trial: 968 people. There are reactions to the injection; otherwise quite low rate of AEs. The rate of severe systemic AEs was similar to the placebo group...6/n

...There were <210 people living with HIV in this group, so it's far too small to draw conclusions, so need for alarm here. Had such a large impact on efficacy because there were 6 people who got Covid-19 (4 in the vaccinated group)...7/n

...Would have been such a different picture without the variant! But it provided some protection against it (prior infection didn't & nor did the Oxford vaccine in a small trial). There was only 1 person with severe Covid-19 in this trial (but remember, not many older people). /8