The chief scientist of the World Health Organization has advised not to mix and match the Covid-19 vaccines that are from different producers. Soumya Swaminathan, the chief scientist, said such a decision should be left to the health authorities. She told in an online briefing on July 12 that the booster shots are a little bit of a dangerous trend. It will become quite a chaotic situation in nations if the public will start deciding when to take the second, third, or fourth dose of vaccine. Swaminathan called mixing of vaccines as a data-free zone but soon clarified her remarks in a tweet.
She said that individuals should not decide to mix vaccines themselves. Public health agencies can do it based on the available data. In the tweet, she wrote data from the studies of mix and match of various vaccines are still awaited. The safety and immunogenicity both require to be evaluated. Certain studies show positive results after mixing vaccines. However, these are just in the preprint stage and require further research to support them.
In some countries, vaccines mixing is seen as an option as there is a shortage of supply of a particular vaccine. But WHO is quite concerned about the situation where people themselves will decide which vaccine to get without the guidance of health authorities. The Strategic Advisory Experts Group of WHO said on vaccines in the month of June that the Pfizer Inc vaccine is possible to be used as the second dose to vaccinate people who initially took AstraZeneca’s first dose. It can only be used if the AstraZeneca vaccine second dose is not available.
Trials for Investigating the Mixing of Vaccines
The University of Oxford led a clinical trial to investigate the mixing and matching of the regimen of Pfizer and AstraZeneca vaccines. The trial has been expanded now to include the Novovax Inc and Moderna Inc vaccines. Vietnam has announced that it would offer a vaccine jointly developed by BioNTech and Pfizer vaccine as a second dose option for all the people who were initially inoculated with the AstraZeneca vaccine.
The mass inoculation campaign of Vietnam in its initial stages, and less than 300,000 people are completely vaccinated so far. The government said that the Pfizer vaccines are going to be prioritized for people who got the AstraZeneca vaccine first shot 8-12 weeks before. Many countries, including Spain, South Korea, and Canada, have already approved the mixing of vaccine doses.