Is COVID-19 Vaccine Mix And Match Safe? WHO Says It's 'Dangerous'

Several countries have taken on the practice of mixing and matching COVID-19 vaccines as they have been found effective in producing strong immune responses among recipients. According to the World Health Organization's chief scientist, however, this trend could be dangerous.

In an online briefing, pediatrician and clinical scientist Soumya Swaminathan said that mixing COVID-19 vaccines is a "dangerous trend" since there was little data available about the health impact, Reuters reported.

"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," Swaminathan said. "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."

In response to the comments made by the WHO's chief scientist, Canadian officials said in another online briefing that the National Advisory Committee on Immunization (NACI) confirmed that doses of Pfizer and Moderna can be used interchangeably when a second dose of the same vaccine is unavailable.

A spokesperson for Health Minister Christine Elliot also said in a statement that Ontario plans to continue following the advice of the NACI, CP24 News reported.

“Ontario continues to follow the advice of the National Advisory Committee on Immunization (NACI) which recommends that it is safe to mix vaccines based on studies from the UK, Spain, and Germany that have found that mixing vaccines is safe and produces a strong immune response,” the statement read.

“The health and safety of Ontarians remain our top priority, and we will continue to monitor the data working with NACI and the federal government,” the spokesperson continued.

Swaminathan later clarified on Twitter that she was warning those who mix and match vaccines on their own.

“Individuals should not decide for themselves, public health agencies can, based on available data,” she wrote.

In a statement addressed to CP24 News, Health Canada and the Public Health Agency of Canada said that the NACI carefully reviewed all factors before giving its recommendation on the practice.

“NACI reviewed all available evidence from ongoing studies monitoring the mixing of COVID-19 vaccines,” the statement read.

It continued, “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 NACI’s expert opinion.”