Mixing and matching Covid-19 vaccines ‘dangerous trend’: WHO’s chief scientist Soumya Swaminathan

"It’s a little bit of a dangerous trend here. We are in a data-free, evidence-free zone as far as mix and match," WHO's chief scientist Dr Soumya Swaminathan said.

The World Health Organization’s (WHO’s) chief scientist Dr Soumya Swaminathan on Monday warned against mixing and matching of Covid-19 vaccines by different manufacturers for the first and second doses, calling it a “dangerous trend” and saying that there was a lack of data about the impact of the process. “There are people who are thinking about mixing and matching. We receive a lot of queries from people who say they have taken one [dose] and are planning to take another one (doses). It’s a little bit of a dangerous trend here. We are in a data-free, evidence-free zone as far as mix and match,” Swaminathan said in an online briefing earlier in the day.

Mixing and matching of Covid-19 vaccines is a method of immunisation using two doses of the shot from different manufacturers. Most vaccines currently in use, including those of Pfizer-BioNTech, Moderna, University of Oxford-AstraZeneca, Bharat Biotech as well as the Russian Sputnik V, are all required to be administered in two doses with the prescribed intervals between the shots differing for each vaccine. Sputnik V also has a single-dose vaccine named Sputnik V Lite and the jab by Johnson & Johnson is a single-dose vaccine too.

“There is limited data on mix and match. There are studies going on, we need to wait for that. Maybe it will be a very good approach. But, at the moment we only have data on the Oxford-AstraZeneca vaccine, followed by Pfizer. It will be a chaotic situation in countries if citizens start deciding when and who will be taking a second, a third and a fourth dose,” she said.

WHO’s director general Tedros Adhanom Ghebreyesus said that the global gap in Covid-19 vaccine supply is “hugely uneven and inequitable.” “Some countries and regions are actually ordering millions of booster doses before other countries have had supplies to vaccinate their health workers and most vulnerable,” Tedros Adhanom Ghebreyesus said.

Swaminathan also stressed the need for equal distribution of the vaccine globally. “We have four countries that have announced booster programs and a few more that are thinking about it. If 11 high and upper-middle-income countries decide that they will go for a booster for their population, or even sub-groups, this will require an additional 800 million doses of vaccine,” she said.

She also said that there is no scientific evidence that a booster shot is definitely needed, especially immediately after the inoculation of the two doses. Instead, she said that the medicine needs to be distributed via the COVAX program to countries that are yet to immunise their front-line workers and the elderly and the vulnerable populations.

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