Sinovac's CoronaVac, in healthcare workers in Uni of São Paulo hospital vs the city: considerable uncertainty, but suggests ca 50% effective despite high level of variants of concern 2 wks after dose 2, rising to around 70% some weeks later...1/n medrxiv.org/content/10.110… Preprint
.For the healthcare workers, "cases" = Covid-19, symptomatic & confirmed. Around 22,000 healthcare workers were vaccinated. If they had symptoms, they left work & got tested... 2/n
...The data are compared with the officially published rates of Covid-19 in the city (presumably not necessarily all symptomatic). Early testing was inadequate as the rate of confirmed cases didn't track with deaths. Later on though the estimates for the city more reliable...3/n
...A major wave of Covid-19 hit the city soon after the healthcare workers (HCWs) had been vaccinated. They estimated how many HCWs you'd expect to get sick, but they caution their model had weaknesses, making the later weeks after vax particularly uncertain...4/n
...They tested a random sample of 142 of the HCWs with Covid-19: they detected variants of concern in 67 (47%) - 57 of those 67 were P1 ("Brazil"), 5 were B.1.1.7 ("UK"), & 5 weren't identified...5/n
...Cautions esp for later weeks, estimated efficacy against symptomatic Covid-19 (large part P1):
- After 2 wks: 50.7% (CI 33-63)
- 3 wks: 51.8% (CI 30-66)
- 4 wks: 68.4% (CI 51-81)
- 5 wks: 73.8% (CI 57-85)

6 unvaxed HCWs hospitalized (1 died) vs 3 part/full vax (0 died)
6/6

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More from @hildabast

16 Apr
Sinovac's CoronaVac in Chile: for Feb-Mar, during major outbreak. Data from National Health Fund, comparisons adjusted for age, gender, region, income, nationality. Fully vaccinated after 14 days was effective; 1 dose wasn't ...1/n
minsal.cl/wp-content/upl… (TY for all the alerts!) Image
...Data doesn't report dosing interval. Covers about 10.5 million aged 16+. 34% of the group was fully vaccinated, but only the CoronaVac data reported here. Comparisons are for people with positive PCR tests: no info on how good that coverage is...2/n Image
...5.1m had 2 doses, 7.6m, 1; 90% are CoronaVac, reported here. Partially vaxed = 14 days after 1 dose; fully = 14 days after 2.

Symptomatic Covid-19:
- Partial: 16.1% (CI 14-18)
- Full: 66.96% (CI 65-69)

Hospitalized:
- Partial: 36.7% (CI 32-39)
- Full: 84.8% (CI 83-87)

3/n
Read 5 tweets
13 Apr
Some things to keep in mind when you see people dumping on "low efficacy" of "Chinese Covid vaccines", particularly based on that single medium-sized trial in Brazil of doses only 2 weeks apart...1/n
...There's the obvious ones: the results of this trial aren't the whole picture - not of the trials that are underway, nor of the way the vaccine is being used (doses more than 2 wks apart)...2/n
...The efficacy against fearsome outcomes was good in this trial - a vaccine that could prevent over 80% of the worst outcomes & reduce the severity in a major way is incredibly needed in a world bereft of enough options...3/n
Read 9 tweets
11 Apr
Preprint on Brazilian trial by @butantanoficial of Sinovac's CoronaVac, 2 weeks apart. Data for 9,823 people who had 2 doses, 12,396 after 1 dose.The P1 ("Brazilian") variant of concern was not circulating in the areas the trial ran...1/n papers.ssrn.com/sol3/papers.cf… HT @josegallucci
...14-day interval seems too close, & immunity may increase over time: they recommend 28 days. Their primary efficacy, unlike other vax trials, includes people who had previous SARS-CoV-2 infection. But this table provides the comparable number: 50.5% (CI 34-63)..2/n
...Their primary efficacy analysis was based on 85 vs 168 people with symptomatic Covid-19. Unfortunately, they don't provide detailed data on symptoms so can't try to see whether this was milder disease than other trials... 3/n
Read 10 tweets
10 Apr
The FDA has said it investigated the blood clot/low platelets cases after J&J vaccine & found no causal association with the vaccine: they're continuing to investigate. abc.net.au/news/2021-04-1… Given the way the EMA's statement of formal investigation is being reported,...1/4
..I went back to EMA press conference to check my tweets. Peter Arlett from EMA said: (at ~40 mins) Since the trial "There have been 3 cases with the J&J vaccine of blood clots associated with low platelets which have some similarities to these cases...2/4
...that we’ve been describing today for AstraZeneca vaccine. However the numbers are extremely small compared to the 4.5 million patients vaccinees that have received the J&J vaccine worldwide.” (~51 mins) "…if you look at those reports of blood clots with thrombocytopenia...3/4
Read 4 tweets
8 Apr
Digging into the detailed EMA report on the AZ vaccine investigation. (The committee vote for their decision was 31 out of 32.) They discuss several hypotheses that have been proposed for the phenomenon, if it's triggered by the vaccine.
ema.europa.eu/en/documents/p…
...1/n
..1st was one from researchers in Germany/Austria, based on studying several of the people: that it's similar to heparin-induced thrombocytopenia ("HITT-like"), & related to Platelet Factor 4. assets.researchsquare.com/files/rs-36235… (preprint)...2/n
...EMA conclusion: there are similarities, so still needs to be investigated. But there are differences too: eg HITT doesn't cause a condition that occurred here (DIC). So they called this unproven...3/n
Read 11 tweets
7 Apr
EMA is listing unusual blood clots with low platelets as a side effect of the AstraZeneca Covid vaccine ema.europa.eu/en/news/astraz… 1/n
...90 cases: 62 with CVST & 24 with splanchnic vein thrombosis (that's abdominal). 18 of 90 people died. It was 90 out 25m, so less than 4 per million. An immune response is a plausible explanation for this, they conclude. 2/n
...MHRA's press conference is delayed, so no word yet there... 3/n
Read 23 tweets

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