The possibility of people receiving Covid-19 shots from different vaccine makers to better boost immunity and maximise safeguards against infection from the rapidly spreading Delta (Indian) variant is being studied, according to the Centre of Excellence in Clinical Virology of Chulalongkorn University.
The result of the study is expected in a few months, according to the head of the centre, Dr Yong Poovorawan.
His research team is working with partners to study administering the vaccine using a combination of Sinovac and AstraZeneca.
The study might show that combining vaccines could lift immunity and guard against infections more effectively than relying on a single brand.
According to Dr Yong, the study involves giving the Sinovac vaccine for the first dose, to be followed by the AstraZeneca vaccine for the second dose to be administered four weeks later.
"In laboratory tests, we have seen very satisfying results. But we are still very concerned about side-effects," he said.
The results of the study will be forwarded to the government, he added.
Dr Yong also stressed the need to slow the rapid transmission of the Delta strain of the virus. He said some people have shown low immunity after receiving two shots of either Sinovac or AstraZeneca and that they need a third shot which, if administered at a proper time, could spur immunity tenfold.
Dr Yong insisted it would be unnecessary for people to go for a test to gauge their levels of immunity after the vaccine shots. Different hospitals employ different methods to run such tests which could throw its accuracy into doubt. On combining vaccines, the professor said the practice is done in many European countries.
However, he noted that Thailand is different because the vaccines made available locally are either inactivated or viral vector types. Combining them may not be as easy as in Europe.
Dr Yong said the world is now facing the problem of vaccines declining in efficacy in the fight against the Covid-19 Delta variant which is threatening to replace Alpha (UK) as the dominant strain in many countries including Thailand in the next four months.
The current vaccines, developed from the original Wuhan strain which first broke out in 2019, may not work well with the mutated variants.
He cited a study in Scotland that found that the AstraZeneca and Pfizer vaccines produced 79% and 60% rates of effectiveness respectively in fighting against Delta variant infection. The effectiveness of both vaccines was higher against the Alpha variant.
Thailand has administered a lot of the inactivated vaccine from Sinovac to its population. Several studies found that its efficacy against the Delta variant may be low, prompting a third jab to be considered.
"With the limited vaccines available, what we should do right now is control outbreaks of the Delta variant. The current vaccines [in Thailand] are effective against the Alpha strain.
"We must vaccinate as fast as possible because all vaccines can reduce the disease's critical symptoms," Dr Yong said.
He warned that people should not lower their guard. They must maintain social distancing, wear a face mask when outdoors and wash their hands regularly.
Dr Yong added that the government's policy to reopen the country's tourism and businesses within 120 days will be impossible to achieve if infection rates remain high.
Dr Supakit Sirilak, head of the Department of Medical Sciences, said there are 614 cases of Delta variant nationwide.
