China’s COVID-19 vaccine has four dramatically different effectiveness rates


Days before the launch of a global deployment with the Indonesian President receiving the vaccine Sinovac Biotech Ltd. On live television, uncertainty swirls over the effectiveness of China’s main vaccine, for which four different protection rate figures have been released in recent weeks.

Indonesia, which is the fastest moving forward in distributing the Sinovac vaccine to its people, said a local trial has shown 65% efficacy against COVID-19. But only 1,620 people in Indonesia participated in this trial – too small for meaningful data.

Turkey said last month that the same vaccine showed 91.25% efficacy in its local trial, which was also too small to draw a sufficient conclusion.

In Brazil, where Sinovac’s largest trial involving more than 13,000 people is underway, duel effectiveness rates have been made public. The company’s local testing partner, Butantan Institute, said last week that the vaccine was 78% effective in preventing mild cases of COVID-19 and 100% effective against severe and moderate infections.

Yet on Tuesday, Butantan said the overall rate, which also includes very mild cases not requiring medical assistance, was actually 50.38%.

The overlap in efficacy data is not unprecedented in the COVID-19 vaccine race – AstraZeneca PLC published two separate rates of protection based on different dosage regimens last month – and all results are above the cutoff of 50% efficiency required by regulators for approval.

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Yet confusion, which arises as several governments pledge to vaccinate their citizens with Sinovac’s vaccine, is fueling skepticism about Chinese vaccines, which have revealed less information about safety and testing than western pioneers. The data fiasco risks further undermining confidence in the clichés President Xi Jinping has vowed to share with the rest of the world as a global public good.

“There is enormous financial and prestige pressure for these trials to massively overestimate their results,” said Nikolai Petrovsky, professor in the College of Medicine and Public Health at Flinders University.

“In many cases, these exaggerations are also politically motivated, as countries that failed to properly control the pandemic now want to overestimate the benefits of vaccines to gain votes and allay local unrest.”

A spokesperson for Sinovac declined to comment on numbers from its trials in Brazil, Turkey and Indonesia and said more data would be released by its Brazilian partner this week.

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The data problem already appears to be delaying regulatory approval of the Sinovac vaccine in some places.

Workers unload Sinovac COVID-19 vaccines from a truck on Tuesday at a warehouse in Banda Aceh, Indonesia. | TBEN-JIJI

“Initially, Sinovac was going to ship the vaccine supply to Hong Kong in January. But they have delayed announcing data from the Phase III clinical trial three times, ”said David Hui, professor of respiratory medicine at the Chinese University of Hong Kong who sits on the financial centre’s COVID-19 advisory committee. Asian. “This would delay the assessment of their application.”

The massive trial in Brazil, which Sinovac says will be where it gets its definitive efficacy data, has come under intense scrutiny.

Observers were taken aback by the first 78% efficiency rate announced by the Butantan Institute. According to the leaked information, the trial saw around 220 participants infected: 160 in the placebo group and almost 60 in the vaccinated group.

If the trial participants were evenly split between the vaccine group and the placebo group, the efficacy rate should rise to 62.5%, said Petrovsky, who is also a research director for Vaxine Pty Ltd., a company that is developing a COVID-19 vaccine.

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External calculations remain speculative unless more data, like the total number of people in the placebo group and the vaccine group, is published in peer-reviewed scientific journals, said Raina MacIntyre, head of the biosafety program at The Kirby Institute at New South University. Wales.

On Tuesday, Butantan explained that 78% was calculated taking into account mild, moderate and severe cases, officials said. When very mild cases are included among the 13,000 volunteers, the figure is 50.4% – 167 volunteers infected in the placebo arm and 85 in the vaccine arm. The shot has been shown to be 100% effective in preventing severe cases.

Brazilian health regulator Anvisa has requested additional data from the Butantan Institute on the Sinovac trial before deciding whether or not to approve the use of the vaccine.

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