A Mix and Match approach in which a Sinovac vaccine shot is administered as the first jab, followed by AstraZeneca as the second jab yields better results against the Delta variant of the coronavirus than two doses of Sinovac, and the same efficacy as two doses of AstraZeneca with a shorter timespan, according to Thailand’s Medical Sciences Department (MSD) and Siriraj Hospital. 

People inoculated with one dose of Sinovac and AstraZeneca for the second dose have higher antibody levels, compared to those inoculated with two doses of Sinovac, and the same levels as those inoculated with two doses of AstraZeneca, according to Dr. Supakit Sirilak, Director-General of the MSD.

However, AstraZeneca for the first dose and Sinovac for the second dose is not recommended.

He also revealed that using AstraZeneca as a third booster dose will increase the immunity levels by up to 11 times, compared to using Sinopharm as the booster dose, which will increases immunity levels by only 2.5 times.

The testing was done using the Plaque Reduction Neutralization Test on six groups of volunteers.

• The first group were those vaccinated with two doses of Sinovac.
• The second group were those vaccinate with two doses of AstraZeneca
• The third group were those vaccinated with Sinovac for the first dose and two doses of AstraZeneca
• The fourth group were those vaccinated with AstraZeneca as the first dose and then Sinovac.
• The fifth group were those vaccinated with two doses of Sinovac and Sinopharm as a third booster shot.
• The last group were those vaccinated with two doses of Sinovac and AstraZeneca as a third booster shot.

Thailand has administered 25.1 million doses of vaccine to date. Of these, 11 million were Sinovac, followed by 10 million doses of AstraZeneca, two million doses of Sinopharm and about 300,000 doses of Pfizer.

Thailand has received a total of 24.5 million doses of Sinovac vaccine from China to date, and is ordering 12 million more doses, even though the initial plan at the beginning of the year is only two million doses of the make. There has been a lot of criticism to order more of the Chinese vaccine, considering studies that prove lower efficacy, especially against the Delta variant, compared to other vaccines.