Canada’s National Advisory Committee on Immunization (NACI) updated its guidance, now recommending that mRNA COVID-19 vaccines like Pfizer and Moderna are the preferred second doses for those who took AstraZeneca as their first.
The change was announced during a press conference on Thursday by Canada’s chief public health officer, Dr. Theresa Tam.
“An mRNA vaccine should now be offered as the second dose for individuals who received a first dose of AstraZeneca or COVISHIELD vaccine,” said Tam, who was also joined by several other public health officials in charge of the country’s COVID-19 response and vaccine rollout.
Tam said that current evidence pointed at a “better immune response” when a first dose of the AstraZeneca vaccine was followed by either Pfizer or Moderna.
“I wish to emphasize that people who received two doses of AstraZeneca/COVISHIELD vaccine should rest assured that the vaccine they received provides good protection against infection, and very good protection against severe disease and hospitalization.”
The new guidance also recommended that mRNA vaccines should be offered to start a vaccine series, unless contraindicated, as well as changes to interchangeability between those shots.
Earlier this month, NACI said the vaccines from Pfizer and Moderna could be mixed and matched safely, though Tam on Thursday appeared to have announced a reversal to that guidance.
According to her, the advisory committee now recommends that anyone who received an mRNA vaccine as their first dose should opt for the same as their second.
However, Tam said that if the same mRNA vaccine wasn’t available for the second dose, another one could be considered and “should be offered” to complete the series.
The NACI’s updates Thursday afternoon come just hours after the Ontario and Quebec provincial governments announced what looks to be contradicting guidance on second doses and vaccine interchangeability.
The Ontario provincial government in a press conference earlier did not raise any issues regarding whether mRNA vaccines could be mixed and matched.
“We will continue to communicate the strong message that the clinical table, that the advice from NACI, that Health Canada has said which is messenger-RNA’s are completely interchangeable,” said Solicitor General Sylvia Jones.
In Quebec, the provincial health minister apologized after the government appeared to show messaging earlier in the week indicating that people who got their first shot of AstraZeneca “should” look to get Pfizer or Moderna as their second because it was more effective than two shots of the same vaccine.
The sudden change in guidance, as well as the contrast with the provincial announcement earlier in the day, left many voicing their frustration and confusion online.
“How can it be that the messaging on vaccines is still so incredibly, frustrating, ridiculously confusing and contradictory?” said Beth Levy on Twitter.
“One of the things I’ll remember the most from this pandemic is how many times NACI made a huge announcement publicly, scared/angered the public, and left the pharmacists and family doctors who actually give vaccines to pick up the pieces,” wrote Dr. Kelly Grindrod, an associate professor of pharmacy at the University of Waterloo.
However, several public health experts have pointed to the updated guidance as the right move in messaging, citing several benefits with taking an mRNA vaccine as a second dose.
Dr. Jennifer Kwan, a family doctor in Burlington, Ont., echoed NACI’s reasoning for preferring those vaccines, but also reassured people of the protection two shots of AstraZeneca held.
University of Toronto infectious disease specialist Dr. Abdu Sharkawy tweeted that getting the second dose of AstraZeneca was still fine, but that the boost to the immunity with mixed vaccines was “outweighing” the short-term effects.
In an email to Global News, University of Toronto epidemiologist Dr. David Fisman said that the announcement was “the right guidance” amid the spread of the Delta COVID-19 variant.
B.C.’s top doctor tried to allay confusion over which vaccine to take on Thursday following the announcement, saying that there was no wrong choice to take for a second vaccine shot.
Provincial health officer Dr. Bonnie Henry said that the recommendation arose from the results of a study in Germany, but that various other studies pointed to the excellent protection given by taking two doses of any vaccine.
“We still know from the information that we’re seeing here in B.C., but also primarily in the U.K., where a lot of AstraZeneca has been used, that vaccine effectiveness is very good for both AstraZeneca and the mRNA vaccines,” she said during a press conference Thursday.
“The bottom line is the very real-world experience and evidence shows us that we have good protection across the board with both vaccines in our community,” she said. “We can be very reassured that two doses of whatever vaccine you receive are safe and effective and work here in B.C.”
— With files from Saba Aziz, Gabby Rodrigues and the Canadian Press