Press conference on results of Brazilian trial of CoronaVac, Sinovac's inactivated vaccine, cleared up the efficacy data & made the complexity of comparing a trial in healthcare professionals with others *really* clear: are they better at self-diagnosing Covid-19 symptoms?...1/n
...That's a central question now: does this trial capture more much "milder" infections than the others we've seen? They're suggesting it does & that drives down the apparent efficacy rate. Here's how the data plays out...2/n
...The trial's definition of symptomatic Covid-19: the first is a slide from the press conference (Portuguese), the second is from the English version of the trial protocol. The primary efficacy endpoint is regardless of whether the person had previous SARS-Cov-2 infection... 3/n
...First the data for the results they reported at the previous press conference. The data are for 9,242 participants. For people needing hospitalization or having severe Covid-19, there were 0 cases with CoronaVac, ...4/n
...Next level is the one they reported last time, the 78% efficacy. It wasn't the primary efficacy outcome. It was for people who needed medical assistance as well as the people hospitalized or severely ill: with a confidence interval from 46% to 90% - a lot of uncertainty...5/n
...This is new: the overall efficacy. They believe while they don't have asymptomatic infections, they have tested for & captured more symptomatic infections than others could. That's a vaccine efficacy rate of 50.38%, CI of 35-62%. So just scraping over the WHO requirement...6/n
...How does this compare? I don't think the press conference revealed age split, but someone who speaks Portuguese might be able to say. Protocol set an overall target of about 10% of people over 60. Oxford/AstraZeneca came in at ~60% efficacy for up to age 55. Which means...7/n
...Brazilian trial, roughly same size & similar-ish confidence intervals, has more people at risk of (severe) Covid-19 & less likely to have strong immune response. Hard to know if it's similar, lower or higher than Oxford. We don't know the efficacy over time for CoronaVac...8/n
...Where does this leave us? I think they made an important point about self-diagnosis of symptoms in a healthcare worker (HCW) trial. The Turkish trial is also for HCWs, similar size, but we don't have the protocol for it, so don't know how otherwise similar...9/n
...Explanation for a previous tweet: when I said "similar CIs", I meant the range was as wide, not the same actual results.

Sources for thread: screenshots of slides from the press conference… Protocol for the Brazilian trial:… 10/10
...PS (always at least 1!!!): This time it's about the numbers. The number for the 2 groups in the slides they gave don't add up to the 9,242 in the slides: they add up to 9,252. I think this means we have to wait for a proper report to be *really* sure about the numbers.
..And here's a good English report of the press conference:…
...About the Brazilian trial for CoronaVac (Sinovac vaccine) for those asking. If participants reported symptoms of Covid-19, they were tested: but if they didn't report symptoms, they weren't.

• • •

Missing some Tweet in this thread? You can try to force a refresh

Keep Current with Hilda Bastian, PhD

Hilda Bastian, PhD Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!


Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @hildabast

11 Jan
Indonesia issued emergency use authorization for Sinovac's CoronaVac; spokesperson for BPOM (drug regulator) said the efficacy rate in the Indonesian phase 3 trial was 65% (trial of 1,600 people).… HT @bayukariastanto ...1/2
...Indonesia's decision was based on the vaccine having above the 50% minimum vaccine efficacy set by the WHO - while the virus is out of control in Jakarta.

Records on this vaccine:… 2/2
...The BPOM spokesperson, Penny Lukito, also announced that CoronaVac has been certified Halal.…
Read 4 tweets
7 Jan
Some results from Brazilian phase 3 trial for Sinovac's inactivated Covid vaccine CoronaVac released at a press conference. Vaccine efficacy for mild symptomatic Covid-19: 78%, similar in people under & over 60 years. 0 moderate/severe/hospitalized... 1/n…
...For background: it's a trial in healthcare workers. The protocol was published here:… Collection of records on this vaccine here:… ....2/n
...Currently buying it from China, US$10 a dose: more than the Oxford vaccine ($3), half of Tozinameran (BNT/Pfizer). However supply of Oxford vax uncertain, whereas they already have drug regulator clearance for local manufacture of CoronaVac... 3/n…
Read 9 tweets
5 Jan
MHRA's (UK drug regulator) 57-page Public Assessment Report on Oxford/AstraZeneca vax is out:… Like Oxford's publication, does not mention phase 3 trials in US & India (& so its serious adverse event), so not clear this is a selective trial report... 1/n
...Quality assessment of the drug & manufacturing facilities based on manufacturer reports & certifications, not MHRA inspections. Presumably as with Tozinameran (BNT/Pfizer vax), this would be done by the European Medicines Agency (EMA)...2/n
...Independent Batch Testing for the vaccine is undertaken UK National Institute for Biological Standards and Control (NIBSC). Temperature requirements confirmed (does not need super-freezing) ...3/n
Read 19 tweets
31 Dec 20
Statement from the UK Joint Committee on Vaccination & Immunisation (JCVI) on why they believe their strategy will achieve maximum impact:… 1/n
...They point out that most of the people who got sick with Covid-19 between 1st & 2nd doses of Tozinameran (BNT/Pfizer vax) did so in the 1st 2 weeks, so the efficacy after 2 weeks was 89% (95% CI 52-97%). But Pfizer stresses... 2/n
...that's only known for people who got their booster shot at 3 weeks, so it's unknown if it stays high for up to 3 months… For the Oxford/AstraZeneca vax, they rely on a subgroup analysis - but the data isn't provided...3/n
Read 5 tweets
30 Dec 20
#tbt This is the amazing Anna Wessels Williams (1863-1954) in the early 1900s. Her sister nearly died in childbirth in 1887: distressed by her treatment, she entered medical school. She moved to lab work in 1894: her 1st major breakthrough came fast ...1/4…
...While her boss was on vacation, she solved the barrier to high-yield diphtheria vaccines. She followed that with a 2-year sabbatical at the Pasteur Institute, creating a rabies vaccine that would be mass-produced in the US. Next was a rabies test in 1905 used for decades...2/4
...She was on the frontlines of the 1918 influenza pandemic, developed a more accurate diagnostic test for trachoma, & co-published a major textbook as well as one of the early successful science books for the public in 1937 ... 3/4
Read 4 tweets
29 Dec 20
Well, dear readers, my take on "the winning formula" for Oxford/AstraZeneca did not age well. According to the Indian manufacturing partner, it isn't the "low"-dose-1st subgroup. It's another subgroup, perhaps a subgroup of a subgroup...… HT @wogboy11 ..1/6
..The sweet spot he says is "a 2-to-3 months’ gap between dose 1 & dose 2". First let's recap their original data. They said intervals didn't make a difference. For the "standard"-"standard" group >8 wks apart vaccine efficacy was 65·6% (24·5 to 84·4). Ditto 6 weeks cutoff ..2/6
...The protocol doesn't limit the possible exploratory subgroup analyses ⬇️: so many ways they could have found a subgroup that hit this mark. Eg half the already-small "low"-dose-1st group had >12 wks apart: sliced off those perhaps? But I don't think that's the main point ..3/6
Read 6 tweets

Did Thread Reader help you today?

Support us! We are indie developers!

This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!