The World Health Organization's chief scientist advised against people mixing and matching COVID-19 vaccines from different manufacturers, calling it a "dangerous trend" since there was little data available about the health impact. "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," Soumya Swaminathan told an online briefing.
"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."
The statement comes amid reports of a recent UK study that said a mix-and-match approach to Covid vaccines--using different brands for first and second doses--appears to give good protection against the pandemic virus. The Com-Cov trial looked at the efficacy of either two doses of Pfizer, two of AstraZeneca, or one of them followed by the other.
All combinations worked well, priming the immune system, the study found. The trial results also hint that people who have already received two doses of AstraZeneca vaccine could have a stronger immune response if they were given a different jab as a booster if recommended in the autumn.