The vaccine against coronavirus developed by Chinese pharmaceutical company Sinovac has proved to be only 50.4 per cent effective in late-stage trials in Brazil, considerably less efficacious than previous announcements suggested.
The data for the Sinovac jab, which is being rolled out to countries outside China and was the first vaccine to be approved in Indonesia, means it is only just effective enough to meed the 50 per cent threshold required to get regulatory approval in Brazil.
The Brazilian government has already preordered millions of doses of the Sinovac vaccine, alongside that which has been developed by AstraZeneca and the University of Oxford.
Brazil is the third worst-hit country in the world in terms of Covid-19 infections, and has been heavily involved in trialling a range of vaccines.
It had initially declared that the Sinovac jab was 78 per cent effective. But it has now disclosed that this only applies to preventing “mild-to-severe” cases, while the vaccine is seen as being 100 per cent effective in preventing serious illness requiring hospitalisation. The overall efficacy rate dropped dramatically when researchers added a large number of “very mild infections” to the data.
The vaccine, which is also awaiting approval in Turkey and Singapore, has produced varying rates of effectiveness in different countries’ trials.
Indonesia found it to be 65 per cent effective against Covid-19, but in trials involving only 1,620 people. Similarly, Turkey found it to be about 91 per cent effective in local clinical trials conducted on a relatively small sample.
Brazil is the only country outside China where the vaccine has been involved in large third-stage trials. They were halted in November after the death of a volunteer, but resumed after doctors established no link between the vaccine and the death.
Sinovac’s vaccine was approved for emergency use in China back in July, initially just for high-risk groups.
Brazil is now reportedly weighing its options between using the Sinovac vaccine and waiting for access to more doses of the AstraZeneca jab. At the same time, the Butantan biomedical centre leading the trials was criticised for initially releasing only partial data.
Brazil has so far recorded more than 9.2 million coronavirus cases and has the second-highest death toll after the US, with 204,726 fatalities.