Canada is standing strong with its decision to use COVID-19 vaccines interchangeably after the World Health Organization (WHO) called it a "dangerous trend." Canada is one of the only countries that allows the mixing and matching of vaccines with the United States and most European Union (EU) countries electing to stay consistent in first and second doses.
The WHO’s chief scientist Soumya Swaminathan said on Monday, "There are people who are thinking about mixing and matching [Covid-19 vaccines]. We receive a lot of queries from people who say they have taken one [dose] and are planning to take another one. 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 [is concerned]."
Swaminathan clarified her remarks in a tweet, saying, "Individuals should not decide for themselves, public health agencies can, based on available data. Data from mix and match studies of different vaccines are awaited - immunogenicity and safety both need to be evaluated."
Canada's National Advisory Committee on Immunization's (NACI) told the Hindustan Times it stands by its decision to offer second doses with interchangeable vaccines and says it's safe. "Current evidence suggests a first dose of the AstraZeneca vaccine followed by a second dose of mRNA vaccine (Pfizer-BioNTech was used in the studies) had a good safety profile," NACI said in a statement.
The NACI reviewed all available evidence from ongoing studies monitoring the mixing of Covid-19 vaccines. The NACI also considered the risk of Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT) associated with Covid-19 viral vector vaccines, Canada’s current and projected mRNA (Pfizer-BioNTech or Moderna) vaccine supply and principles of ethical decision-making. Updated recommendations were based on the current evidence and the NACI’s expert opinion," the spokesperson said.
"Evidence on immune responses produced from mixing Covid-19 vaccines was available from the CombiVacS trial in Spain. Current evidence suggests a first dose of the AstraZeneca vaccine followed by a second dose of mRNA vaccine (Pfizer-BioNTech was used in studies) can boost the immune response at shorter (4-week) and longer (8- to 12- week) intervals," they added.
"Vaccine interchangeability is not a new concept. Similar vaccines from different manufacturers are used when vaccine supply or public health programmes change. Different vaccine products have been used to complete a vaccine series for influenza, Hepatitis A and others," they noted.
According to the Canadian Press 1.3 million Canadians opted for a second dose that was different from their first dose, including Prime Minister Justin Trudeau. Trudeau originally got the AstraZeneca vaccine as his first jab and followed it up with a Moderna mRNA for his second dose.