Canada was an outlier on mixing COVID-19 vaccines, but more countries now following suit

“It is not unusual to mix and match,” said Angela Rasmussen, a virologist with the Vaccines and Infectious Diseases Organization of Saskatoon.

“I think it creates a more resilient situation which is really good overall, because we don’t need to just think about vaccinating everyone in Canada – we need to think about vaccinating everyone in the world.”

An increasing number of countries are considering replacing the various COVID-19 vaccines in their programs as second doses or boosters, in light of supply delays and safety concerns associated with some of the other shots.

Watch | What we know about mixing COVID-19 vaccines:

Bahrain, Bhutan, Indonesia, Italy, Thailand, United Arab Emirates, Uruguay and Vietnam are among those exploring or actively pursuing mixed dosing strategies.

It’s a move increasingly backed by new research, although it is rooted in decades of vaccinology, according to Rasmussen and other vaccine experts.

“Combining vaccines is nothing new,” she said. “There is no reason to expect that it will not be safe.”

“It has already been accepted worldwide for other vaccines,” she said. “Are you asking about the flu shot you get each year? It’s made by different manufacturers.”

For some countries, including Italy and Vietnam, the goal is to provide people vaccinated for the first time with the AstraZeneca-Oxford vaccine with a second dose of an mRNA product, such as Pfizer-BioNTech.

Watch | Travelers with mixed vaccinations say they can’t board some cruises:

Many Canadians who have received mixed doses of the COVID-19 vaccine are having trouble traveling to countries that don’t recognize them as fully vaccinated. Travel bloggers Karen and Brian Houser share how “frustrating” rules affect their travel plans and businesses. 6:34

This is similar to Canadian guidelines from the National Immunization Advisory Committee (NACI), which allow for the interchange of different vaccines at different doses in certain situations.

The advisory recommends that AstraZeneca or mRNA vaccines – Moderna is also approved in Canada – could be offered as a second dose for people who received the first AstraZeneca vaccine.

But the group noted that mRNA options are preferred as a second dose, thanks to emerging safety evidence and the potential for a better immune response.

Mixing doses of Pfizer and AstraZeneca vaccines actually causes a stronger immune response than taking two rounds of AstraZeneca, According to non-peer-reviewed UK research published in June.

lately, As reported by Reuters for the first timeA similar study of nearly 500 medical workers in South Korea also showed that the approach — AstraZeneca first, followed by Pfizer Booster — increased neutralizing antibody levels sixfold, compared to two doses of AstraZeneca.

Canada’s NACI also advocates using the same mRNA vaccines for a second dose if possible, but says another injection of mRNA “can be considered interchangeable” if the first type is not available.

‘acceptable’ approach

When it comes to increasing global uptake of a hybrid vaccine approach, there is a “certain degree of pragmatism,” said Dr. Alexander Wong, an infectious disease specialist at the University of Saskatchewan.

Not every country has “remarkable access” to mRNA snapshots, which is “kind of the bottom line,” he said.

Some countries, such as Thailand and the United Arab Emirates, allow the Pfizer syringe to be used as a booster for those first vaccinated with one of China’s leading vaccines, made by Sinovac and Sinopharm – although there is no research on whether that would raise people’s level of protection.

“We just need some more robust and fast clinical data,” he said.

Wong also says that there is still debate around the world about mixing different brands and technologies.

While some countries adopt a mixed dosing schedule, others completely ban people from entering if they mix in some vaccines – a similar situation with some cruise lines and overseas tourist attractions.