Hundreds Of Health Workers Who Have Been Fully Vaccinated Infected With COVID-19, Sinovac And AstraZeneca Vaccines Are Mixed

JAKARTA - Thailand will use AstraZeneca's COVID-19 vaccine as a second dose, for those receiving the Sinovac vaccine as their first dose to increase protection.

The move is the first publicly announced mix of a Chinese vaccine and a Western-developed vaccine, as a new preliminary study in Thailand raises doubts about the long-term protection of two doses of the Sinovac vaccine.

"This is to increase protection against the Delta variant and build a high level of immunity against this disease", Health Minister, Anutin Charnvirakul, told reporters about adding that the second dose of AstraZeneca would be given three or four weeks after the first injection of Sinovac.

No specific research on blending Sinovac and AstraZeneca has been released yet, but a growing number of countries are seeking different vaccine mixes and matches or delivering a third booster dose, amid fears of new and more infectious variants could escape approved vaccines.

The announcement came a day after Thailand s Health Ministry said 618 medical workers out of 677,348 personnel who received two doses of Sinovac vaccine were infected from April to July, with a nurse dead.

In addition, Thailand is now planning to provide booster injections of imported mRNA vaccines to frontline workers, who are given imported Sinovac before the locally produced AstraZeneca vaccine becomes available in June.

On Monday, a preliminary study in Thailand of 700 medical workers showed Sinovac's level of protection as measured by antibody levels ranged between 60 percent and 70 percent for the first 60 days after the second dose, but that levels continued to fall over time.

"From our research, if our medical staff receive two doses of Sinovac, they should definitely get a third booster shot", said Sira Nanthapisal, a researcher at Thammasat University School of Medicine. However, the researchers have yet to release their full study data.

"They can do it either AstraZeneca or Pfizer when they arrive, and we will continue to monitor their antibodies", Sira continued.

Separately, an AstraZeneca representative declined to comment on Thailand's decision, saying vaccination policy is a matter for individual countries to decide. Meanwhile, Sinovac did not respond to a request for comment on Monday.

Last month, Sinovac spokesman, Liu Peicheng, told Reuters preliminary results from vaccinated blood samples showed a threefold reduction in the neutralizing effect of the Delta variant. And, suggesting a third dose to cause a longer-lasting antibody reaction.

To note, Thailand has imposed strict restrictions from the days since the COVID-19 pandemic last year, amid a wave of highly contagious Alpha and Delta variants, with cases rising to nearly 10,000 per day and record deaths.