Factbox: Countries weigh ‘mix and match’ COVID-19 vaccines

A logo is pictured at the World Health Organization (WHO) building in Geneva, Switzerland, February 2, 2020. REUTERS FILE PHOTO

A growing number of countries are looking at switching to different COVID-19 vaccines for second doses or booster shots after supply delays and safety concerns that have slowed their vaccination campaigns.

The World Health Organization said on July 12 the practice was a “dangerous trend” since there was little data available about the health impact, while Europe’s drug regulator on July 14 made no definitive recommendations on switching doses.

The following are countries that are considering, or have decided to adopt, such a solution:

Cambodia

* Cambodian Prime Minister Hun Sen said on Aug. 1 that a booster shot of AstraZeneca’s vaccine would be offered to people who had previously received two doses of either Sinopharm or Sinovac, while a Sinovac booster shot should be given to Cambodians fully inoculated with the AstraZeneca vaccine.

Denmark

* Denmark’s State Serum Institute, which deals with infectious diseases, said on Aug. 2 that combining AstraZeneca’s vaccine with a second dose from either Pfizer-BioNTech, or Moderna’s shot provides “good protection”.

Germany

* Germany will in September start offering a booster shot of mRNA-vaccines from Pfizer/BioNTech and Moderna to vulnerable individuals such as pensioners and people with weak immune systems, regardless of what vaccines were used for previous inoculations.

Indonesia

* Indonesia is considering offering a booster shot to its healthcare workers immunized with Sinovac’s vaccine, as thousands of them are testing positive for COVID-19.

Russia

* Russia’s Direct Investment Fund (RDIF) said on July 30 that trials mixing a first dose of the Sputnik V vaccine with AstraZeneca’s shot revealed no serious side effects and no subsequent coronavirus cases among volunteers.

It added that the full results of the trial, which was approved on July 26 after being suspended in May by the health ministry’s ethical committee because of a lack of data, would be published this month.

South Korea

* A study from South Korea found in July that a mixed vaccination of an AstraZeneca shot first and then a Pfizer one boosted neutralizing antibody levels six times more than two AstraZeneca doses.

In June, a British study showed that an AstraZeneca shot followed by a Pfizer one produced the best T-cell responses, and a higher antibody response than a Pfizer shot followed by an AstraZeneca one.

Thailand

* Thailand said on July 12 it would use AstraZeneca’s shot as a second dose for people first inoculated with Sinovac’s vaccine, in an attempt to increase protection.

The move is the first publicly announced mix-and-match of a Chinese vaccine and a Western-developed shot.

Vietnam

* Vietnam said on July 13 it would offer the mRNA vaccine jointly developed by Pfizer and BioNTech as a second dose option for those who received the AstraZeneca vaccine as their first dose.