Mixing and matching vaccines not to be decided by individuals: WHO Xinhua 14 Jul 2021, 04:18 GMT+10 GENEVA, July 13 (Xinhua) -- Mixing and matching, the practice of inoculating different vaccines to people, should not be decided by individuals but by public agencies depending on available data, the World Health Organization (WHO) said on Tuesday. While mixing and matching might be interesting for people living in countries where vaccines are in short supply, more studies are needed in order to ensure immunogenicity and safety, a WHO spokesperson cited the organization's Chief Scientist Soumya Swaminathan as saying at a regular press briefing organized by the UN office in Geneva.