Sinovac-AstraZeneca series provides better immunity, says virologist

Sinovac-AstraZeneca series provides better immunity, says virologist

Prof Yong Poovorawan, chief of the Centre of Excellence in Clinical Virology at Chulalongkorn University, explains the use of the Sinovac and AstraZeneca vaccines in series, at the Public Health Ministry in Nonthaburi province on Tuesday. (Screenshot)
Prof Yong Poovorawan, chief of the Centre of Excellence in Clinical Virology at Chulalongkorn University, explains the use of the Sinovac and AstraZeneca vaccines in series, at the Public Health Ministry in Nonthaburi province on Tuesday. (Screenshot)

Use of the Sinovac and AstraZeneca vaccines in series is the best solution available to combat the rapid spread of the Delta variant of the Covid-19 virus, respected virologist Yong Poovorawan said on Tuesday.

Prof Yong, chief of the Centre of Excellence in Clinical Virology at Chulalongkorn University, was speaking at a press conference at the Public Health Ministry in Nonthaburi province.

He said studies showed that a first dose of the Sinovac vaccine followed by a jab of the AstraZeneca vaccine six weeks later could stimulate immunity to a level that could cope with the Delta variant.

The immunity stimulated by two shots of AstraZeneca vaccine was slightly higher, but the two doses had to be 12 weeks apart. That long wait did not suit the present rapid spread of Covid-19 outbreaks through the country, he said.

"With the present rapid outbreaks we cannot wait for 12 weeks. Strong immunity created in only six weeks is in Thailand's highest interests given these local outbreaks," Prof Yong said.

"Besides, Thailand still has only two types of vaccine, inactivated (Sinovac) and virus vector (AstraZeneca). This solution is the best available at present."

Prof Yong said that two doses of the Sinovac vaccine stimulated immunity to the same level as in people who recovered from Covid-19, but this level could not handle the Delta variant.

The inactivated Sinovac vaccine was based on the early Wuhan virus, he said.

"The efficacy of all vaccines developed for the Wuhan strain drops when it comes to the Alpha and Delta variants," he said.

One dose of the AstraZeneca vaccine could not cope with the Delta variant either, he said.

"To speed up immunity stimulation among Thais amid such rapid virus mutation, researchers looked into the administration of the inactivated vaccine (Sinovac) as the first jab and the virus vector vaccine (AstraZeneca) as the second.

"Studies showed that the immunity stimulation was higher than expected," Prof Yong said.

"Sinovac and AstraZeneca vaccinations in series is likely to better prevent virus mutation," he said.

His media briefing at the Public Health Ministry followed the National Communicable Disease Committee's resolution to use the Sinovac and AstraZeneca vaccines in series.

Prof Yong said the Sinovac-AstraZeneca vaccination series had been administered to more than 1,200 people in Thailand, most of them at King Chulalongkorn Memorial Hospital.

Officials used the MorProm app to follow up the recipients' condition, and no one reported any severe adverse impact, he said.

"No one among the 1,200 people developed any serious side effect. The information from the MorProm app proves that the mixed administration of both vaccines is safe in real life," he said.

Thailand logged 56 new Covid-19 fatalities and 8,685 new cases over the past 24 hours and ranked 60th by the number globally, with 353,712 accumulated Covid-19 cases.

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