China's Sinovac plots pivotal COVID-19 vaccine trial in Brazil after positive phase 2

Vaccine vaccination
China's Sinovac Biotech says its inactivated COVID-19 vaccine induced neutralizing antibodies in a phase 2 trial. (Pixabay)

Another Chinese company is touting an early clinical win for its experimental COVID-19 vaccine.

Two doses of Sinovac Biotech’s COVID-19 vaccine candidate, dubbed CoronaVac, induced neutralizing antibodies 14 days after vaccination. More than 90% of the 600 healthy volunteers in the phase 2 part of the phase 1/2 study showed that immune response, the Nasdaq-listed company said Saturday.

Data from the phase 2 study, as well as a phase 3 study protocol, will be submitted to China’s drug regulators to clear the way for final testing, the company added.

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The shot uses inactivated virus to stimulate an immune response, a proven method—unlike most vaccine candidates racing ahead in the U.S. But inactivated vaccines are more time-consuming to produce than the next-gen shots based on the virus's genetic material.

Last week, Sinovac penned a deal with Brazilian immunobiologic producer Instituto Butantan to run the vaccine’s phase 3 in Brazil. In return, Instituto Butantan gains license to the investigational shot in its home country.

Detailed phase 2 results are not available right now, though Sinovac said it will share them later through academic publications. For example, the exact level of neutralizing antibodies CoronaVac triggered was not clear.

At this point, the scientific community doesn’t yet know what level of neutralizing antibodies can protect people against a COVID-19 infection if at all. Testing a vaccine’s efficacy in a phase 3 trial usually requires thousands of people in places where the virus is still circulating. However, despite a new spike of cases in Beijing, COVID-19 is largely contained in China, making it difficult to run such a trial there.

RELATED: What's needed to prove a COVID-19 vaccine works—and are top players across 3 continents there yet?

Sinovac’s vaccine is based on inactivated whole virus, a mature vaccine technology that’s also been used to produce vaccines against influenza and polio. In contrast, most Western COVID-19 vaccine players are working on next-generation platforms that involve using the DNA or RNA of the novel coronavirus.

Compared with those newer technologies, inactivated vaccines take longer to manufacture, because live virus must be grown in cultures and then inactivated. Sinovac said it’s building a commercial plant in China that’s expected to make up to 100 million doses of CoronaVac a year.

CoronaVac is among five China-developed COVID-19 vaccines that have entered clinical testing. Leading the race is CanSino Biologics’ adenovirus-based recombinant vaccine, which was the first in the world to enter a phase 2 trial and the first to report first-in-human data in a peer-reviewed journal. State-run Sinopharm has two inactivated shots from its biological research institutes in Beijing and Wuhan. The Chinese Academy of Medical Sciences’ Institute of Medical Biology also has an inactivated version.

In contrast, none of the five programs recently picked by the Trump administration’s “Operation Warp Speed” as the most likely to succeed in a short time frame is based on the inactivated vaccine technology.

Among them, AstraZeneca and University of Oxford’s adenovirus-vectored vaccine, AZD1222, also known as ChAdOx1 nCoV-19, is also slated for a phase 3 trial in 2,000 volunteers in Brazil.

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