The media has recently reported that a physician associated with the World Health Organization (WHO) suggested that the mixing of vaccines was a ‘dangerous trend’. This was not an official statement by the World Health Organization. The statement was made at a session unrelated to vaccine mixing and was taken out of context by news agencies. This quote was in relation to a question about the need for COVID-19 booster shots. Scientists do not know yet if booster shots are necessary for additional or sustained protection. Remarks by WHO officials were not about Canada’s COVID-19 vaccination program nor did they contradict recommendations by the National Advisory Committee on Immunization (NACI) and the Public Health Agency of Canada (PHAC). Peel Public Health has full confidence in federal and provincial guidance that supports the mixing of mRNA vaccines (Pfizer and Moderna), as well as mixing AstraZeneca and an mRNA vaccine. Vaccine interchangeability allows residents of Ontario to receive timely second dose coverage in the current environment where COVID-19 variants put the health of residents at risk and vaccine supply in Canada is variable. Ontario continues to follow the advice of NACI which recommends that it is safe to mix these vaccines based on studies from the UK, Spain and Germany. These studies have shown that mixing vaccines is safe and produces a strong immune response.
https://www.womenscollegehospital.ca/covid19/covid-19-vaccine-multi-language-information-sheets