Days before a global rollout begins and the Indonesian President delivers the vaccine from Sinovac Biotech Ltd. on live television, there is uncertainty about the effectiveness of the leading Chinese shot, for which four different protection rates have been released in the past few weeks.
Indonesia, which is the fastest to distribute the Sinovac shot to its population, said a local study showed 65% effectiveness against Covid-19. In Indonesia, however, only 1,620 people took part in this study – too small for meaningful data.
Turkey said last month that the same vaccine had 91.25% effectiveness in its local study, which was also too low to draw a sufficient conclusion.
In Brazil, where Sinovac’s largest study involving more than 13,000 people is conducted, duel effectiveness rates have been published. The company’s local study partner, the Butantane Institute, said last week that the vaccine was 78% effective at preventing mild cases of Covid-19 and 100% effective against severe and moderate infections.
However, on Tuesday, Butantane said the overall rate, which includes very mild cases that didn’t require medical attention, is actually 50.38%.
Overlapping efficacy data is not unprecedented in the Covid-19 vaccine race – AstraZeneca Plc released two separate protection rates based on different dosage regimens last month – and all results are above the 50% efficacy threshold required by regulators for approval.
However, the confusion that arises when multiple governments commit to vaccinating their citizens with Sinovac’s shot fuels skepticism about Chinese vaccines, which have disclosed less safety and testing information than Western front-runners. The data kerfuffle could further undermine confidence in recordings President Xi Jinping has pledged to share as a global public good with the rest of the world.
“There is tremendous financial and prestigious pressure on these studies to massively exaggerate their results,” said Nikolai Petrovsky, professor in the College of Medicine and Public Health at Flinders University.
“In many cases, such exaggerations are politically motivated as well, as countries that haven’t properly controlled the pandemic now want to overestimate the benefits of vaccines in order to win votes and allay local unrest.”
A Sinovac spokesman declined to comment on the numbers of his trials in Brazil, Turkey and Indonesia, saying more data would be released from his Brazilian partner this week.
The data problem appears to be holding back regulatory approval for Sinovac’s vaccine in some places.
“Sinovac originally planned to deliver vaccine supplies to Hong Kong in January. However, the release of the Phase III clinical trial data has been delayed three times,” said David Hui, professor of respiratory medicine at the Chinese University of Hong Kong, who sits on the Covid-19 advisory board Asian financial center. “That would delay the evaluation of your application.”
The massive Brazil study that Sinovac has announced is receiving its final efficacy data has been scrutinized.
Observers were delighted with the first 78% effectiveness rate announced by the Butantane Institute. According to the published information, around 220 participants were infected in the study: 160 in the placebo group and nearly 60 in the vaccinated group.
If the study participants were evenly split between the vaccine and placebo groups, the effectiveness rate should be 62.5%, said Petrovsky, who is also director of research at Vaxine Pty Ltd. is, a company developing a Covid-19 vaccine.
External calculations remain speculative unless additional data, such as the total number of people in the placebo group and the vaccinated group, are published in peer-reviewed scientific journals, said Raina MacIntyre, director of the biosecurity program at the university’s Kirby Institute of New South Wales.
On Tuesday, butantane stated that the 78% was calculated taking into account the light, moderate, and severe cases. If very mild cases are included among the 13,000 volunteers, the number is 50.4% – 167 infected volunteers in the placebo arm and 85 in the vaccine arm. The shot was found to be 100% effective in preventing severe falls.
Brazilian health agency Anvisa requested additional data on the Sinovac study from the Butantane Institute before deciding whether to approve the vaccine for use.
(Except for the headline, this story was not edited by GossipMantri staff and published from a syndicated feed.)