Cocktail experiment: Thailand to try mixed Sinovac, AstraZeneca shots

In a first such official attempt, Thai authorities to combine Chinese, Western-developed shots to increase protection against highly transmissible COVID variants

For those who have already taken two doses of the Sinovac vaccine, Thailand plans to administer mRNA boosters as well.

Thailand has announced plans to administer AstraZeneca’s viral vector COVID vaccine as a second dose for people who were given Chinese pharma firm Sinovac’s inactivated virus vaccine as their first dose. The aim is to increase protection against highly transmissible variants of the virus, a Reuters report said.

If implemented, it will be the first publicly announced mix-and-match of a Chinese vaccine and a Western-developed shot, said the report. “This is to improve protection against the Delta variant and build high level of immunity against the disease,” it quoted Thai Health Minister Anutin Charnvirakul as saying.

Breakthrough infections

Thailand and other Southeast Asian nations such as Indonesia have witnessed breakthrough infections in those inoculated with Sinovac’s vaccine. The cases have been particularly high among healthcare and other frontline workers. The majority of these populations were given Sinovac’s shots after February.


AstraZeneca’s viral vector vaccine has been more widely available in Thailand only since June. The authorities hope to fortify the inoculation of the healthcare workers with a second jab of AstraZeneca’s candidate.

Also read: COVID vaccine supply crunch may force hundreds to miss 2nd dose deadline

The Reuters report, quoting the Thai Health Ministry, said 618 medical workers out of the 677,348 who received two doses of Sinovac, caught COVID-19, from April to July. One nurse has died and another medical worker is in critical condition, it added.

Booster shots, too

For those who have already taken two doses of the Sinovac vaccine, Thailand plans to administer mRNA boosters as well.

Thailand recorded 8,656 infections and 80 deaths on Monday. Overall, it has seen 345,027 cases and 2,791 deaths, mostly from an outbreak caused by the highly transmissible Alpha and Delta variants, said Reuters.

From the beginning of this week, the country has implemented its toughest-ever COVID curbs in more than a year in capital Bangkok and surrounding provinces. These include new restrictions on movement and gatherings as well as suspension of services by airlines and bus companies.

Leaked memo

Last week, a leaked document from the Health Ministry had prompted calls in Thailand for healthcare works to be given a booster shot of an mRNA vaccine. The internal memo had reportedly included a comment saying such a step may dent public confidence in the Sinovac vaccine.

The memo, whose authenticity the Health Minister confirmed, included an unnamed officer’s remark that giving a booster shot of Pfizer-BioNTech’s COVID vaccine would be “admitting that the Sinovac vaccine is not effective”.