Canada’s chief science adviser issues warning about B.C.’s ‘experiment’ with vaccine timing

British Columbia’s decision to extend to four months the interval between first and second doses of three different vaccines amounts to a “population level experiment,” said Mona Nemer, Canada’s chief science adviser.

“I think that it’s possible to do it. But it amounts right now to a basically population level experiment. And I think it needs to be done as we expect clinical trials to be carried out,” Nemer told CBC News Network’s Power & Politics today. 

Nemer told host Vassy Kapelos that the data provided so far by Moderna and Pfizer on their vaccines were gathered when the first and second doses of the vaccines were being spaced three to four weeks apart, not three to four months apart. 

“I think it’s really important that we stick with the data and with the great science that give us these fantastic vaccines, and not tinker with it,” she said. 

If provinces want to find out if the interval between the first and second doses can be extended to 16 weeks, she said, those provinces should conduct proper clinical trials by registering participants and explaining to them the possible advantages and disadvantages of taking part.

She said that while such trials might show that it’s safe to extend the interval to four months, Canada is not there yet.  

“For now, we simply don’t have enough data that tells us this is an effective strategy, particularly when we think that we have variants of the virus that are emerging that are not as well recognized by the vaccine,” Nemer said. 

“Partial immunity is something that people need to be very wary of. And it’s probably best to just vaccinate as recommended and as studied for now.”

Watch: Mona Nemer: ‘partial immunity is something that people need to be very wary of.’:

B.C. extends the interval

Earlier today, B.C.’s Provincial Health Officer Dr. Bonnie Henry announced that the province would be extending the interval between doses of the Moderna, Pfizer and Oxford-AstraZeneca vaccines to 16 weeks.

“From the very early days, we made sure that every single dose is recorded and we knew who got what vaccine when, and part of this feeds into our evaluation of vaccine effectiveness,” Henry said.

“We have seen that the vaccines we have here in B.C. are safe and they provide a very high level of real world protection with the initial dose.”

Henry said data from the B.C. Centre for Disease Control, and countries around the world, shows “miraculous” protection of at least 90 per cent from the first dose of the Moderna or Pfizer-BioNTech vaccine.

NACI guidance

Henry said the B.C. CDC has been exchanging data with colleagues across the country and similar results are coming from Quebec, as well as from the U.K., Israel and other countries.

She also said the National Advisory Committee on Immunization (NACI) has been looking at the issue and will be issuing a statement on the matter in the near future.

As of March 1, however, the advice NACI is providing on its website says that the interval between the first and second shots of the Moderna vaccine should be four weeks, the interval for Pfizer should be three weeks and the interval for the Oxford-AstraZeneca vaccine should be 12 weeks. 

The head of Moderna’s Canadian operations, Patricia Gauthier, told Kapelos Monday that the company’s own trials, and the conditions under which the vaccine was approved by Health Canada, are tied to a four week interval.

“That being said, we’re in times of pandemic and we can understand that there are difficult decisions to be made,” Gauthier said. “This then becomes a government decision. We stand by the product monograph approved by Health Canada, but governments … can make their own decisions.”

Gauthier said she is not aware of any studies done or led by Moderna on what happens when the interval between the first and second doses is changed from four weeks to four months.