NACI accused of contributing to confusion, hesitancy over 'preferred' vaccines guidance


The National Advisory Committee on Immunization is being accused of creating confusion about COVID-19 vaccines after it restated that mRNA vaccines were “preferred” over the viral vector ones.

On Monday, NACI doubled down on its position that the Pfizer-BioNTech and Moderna vaccines were “preferred” over the Johnson & Johnson and AstraZeneca shots, and that Canadians should weigh the risks before they decide which one to receive.

The viral vector AstraZeneca and Johnson & Johnson doses have been linked to an extremely rare and potentially life-threatening blood-clotting syndrome called vaccine-induced immune thrombotic thrombocytopenia (VIITT). The risk for developing this syndrome is estimated to be anywhere from one case in 100,000 doses to one case in 250,000. 

The Johnson & Johnson vaccine has been approved for use by Health Canada, but the agency said it was holding the first 300,000 doses in order to conduct further quality assurance tests after one of its ingredients was discovered to have been made in a problem-plagued vaccine manufacturing facility in the States.

While the vaccine-related blood-clotting syndrome is very rare, with only seven reported VIITT cases in all of the approximately 1.7 million doses of AstraZeneca that have been administered in Canada so far, the committee’s vice-chair Dr. Shelly Deeks said it should be taken into consideration.

“The viral vector vaccines are very effective vaccines, but there is a safety signal, a safety risk… And the issue with the safety signal is that although it is very rare, it is very serious,” she said. “Individuals need to have an informed choice to be vaccinated with the first vaccine that’s available, or to wait for an mRNA vaccine.”

Viral vector vaccines use a weakened or attenuated common cold virus, which is not the same SARS-CoV-2 virus that causes COVID-19, and manipulate it so it can’t replicate or cause illness. The SARS-CoV-2 spike protein is then attached to the vector virus so the immune system can learn to recognize it and fight off a potential infection if it’s confronted with the real coronavirus and its spike protein in the future.

The mRNA vaccines, on the other hand, use a technology that teaches the body’s cells to make a protein that can trigger an immune response to ward off an infection by the SARS-CoV-2 virus.

This latest announcement from NACI appears to contradict Health Canada’s oft-repeated guidance to Canadians that the best vaccine is the first one available to them.

-- with files from CTV News and The Canadian Press --