World Health Organization’s chief scientist Soumya Swaminathan on Monday advised against mixing and matching coronavirus vaccines from different manufacturers, calling it a “dangerous trend”, reported Reuters. “We are in a data-free, evidence-free zone as far as mix and match,” Swaminathan said at 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.” Mixing and matching Covid-19 vaccines is a method of immunisation in which two doses of the shot from different manufacturers are given to a beneficiary. Most vaccines currently in use, including those of Pfizer, AstraZeneca and Bharat Biotech, are all required to be administered in two doses with the prescribed intervals between the shots differing for each vaccine.