Editor’s note: A previous version of this story attributed comments to Dr. Danuta Skowronski instead of the report she co-authored.
Anyone in British Columbia who received two doses of AstraZeneca’s COVID-19 vaccine can now get a booster six months after they received their second shot, B.C.’s top doctor said Monday.
People with two doses of AstraZeneca have shown waning levels of protection from infection, although it still offers strong protection against severe illness, Dr. Bonnie Henry said.
“This may be sooner than other healthy adults in the community where we know there’s very good, strong protection that’s lasting well,” she said.
Last week, health officials announced plans to provide booster shots to anyone who wants one six to eight months following their second dose. People who have been designated clinically extremely vulnerable, who received two doses of AstraZeneca, and who work in acute care would be first, followed by the general population starting next year.
However, several new studies indicate that a booster may not yet be necessary for those who received either two doses of mRNA or a mix of AstraZeneca and mRNA vaccines, if those doses were administered at an interval of eight to 12 weeks.
Brian Grunau with the University of British Columbia’s Department of Emergency Medicine said early results from a study of paramedics across Canada show that longer vaccine-dosing intervals lead to enhanced immune responses.
“The interaction between vaccine dosing intervals may play a role in the timing and need for third vaccines,” he said.
“Our data suggest that the immune response is prolonged in those who have longer vaccine dosing intervals, so this may make individuals who have longer dosing intervals less required of a booster shot earlier on.”
Other researchers aren’t convinced that booster shots are needed for everyone yet.
A study published online Oct. 26, with Henry and Dr. Danuta Skowronski of the BC Centre for Disease Control among the authors, found that the immune response from two shots administered at extended intervals is robust, and that “the need and timing of a third dose warrant serious reflection by decision-makers.”
Dr. Gaston De Serres, also a study co-author and an epidemiologist with the Institut National de Santé Publique du Québec, told Global News the data in Canada shows two doses of the vaccine are still working.
“I think that what we found in our study was showing that there was pretty much no decline in protection during the first six months after the second dose,” he said. “And therefore, the justification for going to a third dose for everybody over 12 years of age must be outside of what we observe in Canada.”
De Serres highlighted the need to focus resources on getting vaccines to the developing world.
“The risk of mutations and the appearance of new dangerous variants will depend upon the number of people being infected and if there is no vaccine, obviously that’s a great opportunity for the virus to infect people and eventually acquire mutations that could be quite nasty.”
On Friday, he said public health officials have focused on preventing hospitalizations and deaths since the beginning.
“Well, to change that focus might be clearly something that has to be evaluated quite carefully because of this question about letting developing countries have access to the vaccines.”
Henry said the province needs to focus on boosters while also considering the bigger picture.
“We need to be able to be part of our global community and make sure people around the world are vaccinated, and we need to protect those people who need it right now,” she said.
— with files from Leslie Young and Carolyn Jarvis