The vaccine from Chinese pharmaceutical company Sinovac is only 50.4% effective, according to updated data from a Brazilian trial.
Sinovac’s vaccine uses inactivated virus particles to trigger an immune response. Both the Sinovac vaccine and the Oxford vaccine have requests for emergency use in Brazil which are expected to soon to be granted.
This new number is lower than what was suggested last week by Butantan Institute, which distributes 65% of the vaccines in the country, and is running the trials. They had reported that the vaccine was 78% effective in “mild-to-severe” COVID cases, but reported on Tuesday that this number had not included cases with very mild COVID symptoms.
Interim results from late stage trials in Turkey and Indonesia reported that SinoVac was 91.25% effective and 65.3% effective, respectively.
All of these discrepancies show just how hard to it is to compare the effectiveness of vaccines as measured by different trials in different countries. Other countries only count cases of COVID which generate obvious symptoms; including cases which are almost asymptomatic will lower the reported effectiveness.
However, there has been concern that the Chinese vaccine trials have not been subject to the same level of scrutiny and transparency as those in the West. Conversely, claims that the Russian Sputnik vaccine has a 95% effectiveness have been met with some suspicion, especially given its haphazard roll-out, which combined a trial (now cut short) with a release for emergency use.
Source:BBC News
