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Controversial Thai Virologist Calls Covid-19 Vaccine Mixing ‘Highly Effective’

Dr. Yong Poovorawan, director of the the Center of Excellence in Clinical Virology at Chulalongkorn University.
Dr. Yong Poovorawan, director of the Center of Excellence in Clinical Virology at Chulalongkorn University has been criticized for being a government "Sinovac salesman".

Thailand’s top – and controversial – virologist claims that a vaccine cocktail of Sinovac and AstraZeneca is highly effective in preventing Covid-19 infections.

Dr. Yong Poovorawan, director of the Center of Excellence in Clinical Virology at Chulalongkorn University, said Monday that two doses of inactivated virus vaccine helps immunity rise to an average level of 100 units.

If two doses of a vector vaccine are given 10 weeks apart, the immune system will rise to 900 units. If the vaccines are alternated, inactivated virus followed by the vector virus type three to four weeks apart, the recipient achieved a high immunity of 700 units.

“We can’t wait 12 weeks in this outbreak where the disease is spreading fast,” Yong told the media in an earlier July 13 interview, defending the controversial decision to mix-and-match vaccines. “But in the future, if there are better, improved vaccines… we will find a better way to manage the situation.”

Even better results were shown with a third booster shot of vaccine, said Yong, who has attracted intense social media criticism over what critics see as his defense of the Chinese-made Sinovac vaccine. An engineering student was arrested for editing Yong’s Wikipedia page to call him a “Sinovac salesman” for the government.

Two doses of the inactivated virus vaccine, followed by the virus vector vaccine, as front-line medical personnel are now doing, has been found to provide an average immunity boost of 10,000 units.

Dr. Yong added that the center is currently conducting in-depth research into its ability to block each variant of the virus, including delta.

From past data, the delta strain evades immunity and higher levels of immunity are needed, until a vaccine that addresses the specific strain or second-generation vaccines are available.

The World Health Organization’s chief scientist Soumya Swaminathan earlier this month called the mix-and-match strategy a “dangerous trend”.

“We are in a bit of a data-free, evidence-free zone as far as ‘mix-and-match'”, she said, later clarifying she was referring only to individuals choosing to mix vaccine types. She had no direct comment on government plans to do so.

The National News Bureau of Thailand contributed to this report.