Sinovac Biotech’s CoronaVac vaccine above 50 per cent efficacy, says Brazilian institute

Simone McCarthy
·4-min read

A Covid-19 vaccine made by Sinovac Biotech was found to be more than 50 per cent effective based on analysis of its late-stage trial conducted in Brazil, Reuters reported, citing Sao Paulo health officials.

The announcement, made by Brazilian trial partner Butantan Institute on Wednesday, marks a major step forward for the Chinese-developed jab – one of several front runners in the global race for a Covid-19 vaccine – whose doses have already been booked by countries around the world.

In announcing that the vaccine, which is called CoronaVac, had met the efficacy threshold set by Brazilian health regulator Anvisa, Butantan also said that Sinovac had asked for a delay releasing precise efficacy data for up to 15 days while the company consolidates data from global trials, according to Reuters, which quoted Butantan director Dimas Covas as saying that none of those in the trial developed a severe case of Covid-19.

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CoronaVac began its phase three trials in Brazil in July, and since expanded to other overseas trial sites including Turkey and Indonesia. Brazil is the first site to complete and report results from its trial.

The Sinovac vaccine provides a potentially significant advantage in the drive to get vaccines to all corners of the world, as it uses an inactivated virus platform and can be stored at normal refrigerator temperatures. This may make the two-dose vaccine more accessible for developing countries, as compared with vaccines that require storage or transport at freezing temperatures, like the mRNA vaccine from Pfizer and BioNTech.

A handful of countries already have purchase agreements with Sinovac for doses, including Brazil, Turkey, Indonesia, Singapore, and Chile. Hong Kong is also set to receive 7.5 million doses of CoronaVac.

Brazil is expected to purchase 46 million doses of CoronaVac, with the first batch delivered in November. Anvisa, Brazil’s National Health Surveillance Agency, on Monday issued Sinovac a certificate of good manufacturing practices, following an evaluation by Brazilian inspectors of the company’s CoronaVac vaccine factory in China.

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The release of trial results from Butantan Institute follows an announcement of interim data from a clinical trial of an inactivated vaccine from another Chinese firm, state-owned Sinopharm.

The UAE and Bahrain earlier this month approved a vaccine developed under Sinopharm for general use, citing 86 per cent efficacy in an interim analysis of a phase three trial. Full results have yet to be released.

The Sinovac vaccine and two under Sinopharm received emergency use authorisation in China in July, but both have yet to receive regulatory approval there for general use. In a press briefing on Saturday, officials from the National Health Commission said regulators were receiving phase three trial data from vaccine makers on a rolling basis.

Meanwhile, an experimental coronavirus vaccine developed by the Chinese Academy of Sciences has been found to be safe and trigger an immune response in early and mid-stage clinical trials, researchers said on Tuesday.

The candidate, developed in collaboration with Anhui Zhifei Longcom Biopharmaceutical, is the fifth vaccine developed in China to have entered final-phase trials, and the first Chinese candidate to do so that employs the “protein subunit” method – using a purified piece of the virus selected for its ability to stimulate immune response.

Named ZF2001, the vaccine caused no severe adverse events among 950 participants in phase 1 and 2 trials, according to researchers, and produced neutralising antibodies – a critical component of immune defence – in at least 93 per cent of participants who received a three-dose course of the experimental vaccine.

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ZF2001 also provoked “moderate” cellular immune response, another arm of the body’s defence that is thought to play a role in countering the coronavirus that causes the disease Covid-19, the researchers said in a paper yet to receive peer review.

“Our findings indicated that [the receptor binding domain]-based protein subunit vaccine is safe and immunogenic. Further clinical trials should be performed to investigate its protective efficacy,” said the authors, who included George Gao, director of the Chinese Centre for Disease Control and Prevention.

The scientists cautioned that although the levels of neutralising antibodies were higher than those seen in patients recovering from Covid-19, the vaccine’s efficacy against the coronavirus was still unknown.

Additional reporting by Robert Delaney

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