Third vaccine shot may be necessary to combat Delta variant

The head of the Department of Disease Control says a third vaccine dose may be needed to protect against more infectious Covid-19 variants. Opas Karnkawinpong says officials are studying if it is safe to vaccinate people with different brands following the first dose, but says it’s too soon to say.

“Knowledge (about the virus and the vaccines is updated) constantly so we need to wait until we have sufficient information to support any new decisions to make. We have a team that is following up on this and will decide what will be the most suitable (for Thailand’s situation).”

The Bangkok Post reports that a similar study is being carried out by renowned virologist Yong Poovorawan, from the Centre of Excellence in Clinical Virology at Bangkok’s Chulalongkorn University. According to Yong, the Delta variant of Covid-19, first detected in India, is likely to become the dominant strain in Thailand as case numbers increase. He says vaccines need to provoke a much higher immune response in order to protect against the variant.

“While most cases here are now found to be of the Alpha variant, the Delta variant will in the next few months dominate in Thailand, given the (mutation) of this particular virus variant.”

According to Yong, studies involving both the Pfizer and AstraZeneca vaccines show they are less effective at protecting against the Delta variant. 14 days after the first dose, Pfizer was shown to be 79% effective, compared to 60% with AstraZeneca. Both vaccines showed efficacy of 92% and 73% respectively against the original, Alpha, variant of Covid-19. Yong says the duration between the first and second AstraZeneca dose may need to be shortened in order to boost protection against the Delta variant. He adds that in the case of other vaccines which have shown lower efficacy, booster shots may be needed until new vaccines that can cope with the Delta variant are developed.

His comments come as officials express concern over an outbreak of the Beta variant in the south of the country, which studies have shown is also more resistant to current vaccines.

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SOURCE: Bangkok Post