As of April 8, 2021, more than seven million doses of the COVID-19 vaccine have been administered in Canada, and approximately 17 percent of the population has received at least one dose.
While the majority of Canadians are still waiting for their dose, only 12 percent of Canadians said they have no plans to be vaccinated, according to a recent Army survey. Achieving a herd immunity would require 53 to 84 percent of Canadian immunity if a significant portion of the population is immune to vaccination by vaccination or natural infection, taking into account the strongest variants and the rate at which one can spread.
How long immunization will last and whether Canadians need shots annually against COVID-19 is not resolved.
Several factors determine the immune response to a vaccine – including age, sex, genetics, comorbidities, behavior, nutrition and environment – so that it may differ from person to person.
Yet clinical trials, and now actual data, show that Pfizer-BioNTech and Moderna vaccines are at least 90 percent effective after two or more weeks of vaccinations of the recommended doses.
COVID-19 variants ‘definitely a concern’
Yanet Valdez Tejeira, a Vancouver immunologist, infectious disease expert and volunteer chief at COVID-19 Resources Canada, says researchers are currently extrapolating data from clinical trials that began last year to see how long the vaccine against COVID-19 vaccines will last. duration.
“I know for sure that at least one vaccine, Pfizer-BioNTech, confirmed on April 1 that the vaccine provides protection that lasts at least six months after the second dose,” Tejeira said.
She is hopeful that researchers will follow the participants’ years to evaluate the long-term effects and efficacy of the vaccines, but current data suggest that immunity may last longer than the guaranteed period of six months.
Health Canada says the exact duration of the immunity to the vaccine is unknown and researchers are still looking at the data as it enters.
“We will continue to work with partners to monitor evidence on the long-term effectiveness of our authorized vaccines, and how they are protected from variants of concern,” said Anna Maddison, spokeswoman for the Health Channel and the Health Council of Canada. .
Although the vaccines have been effective in preventing serious diseases, hospitalization and death due to the original strain of the virus, studies have only now begun to account for the efficacy of the vaccine against variants of COVID-19.
“The effectiveness of vaccines against emerging variants is certainly a source of concern, and depends on the type of vaccine,” Tejeira said. “The Pfizer one, for example, appears to be quite effective against the alarming B.1.351 variant [from South Africa] of the virus. On the other hand, it appears that AstraZeneca’s vaccine is less effective against the same variant. ‘
Researchers are concerned that if more people become infected continuously, more variants will emerge against which the vaccines may not be able to protect.
Does a stronger immune response to the pathogen mean longer immunity?
An effective immune response of a vaccine means that the body is protected against a virus without hurting its own cells by causing inflammatory reaction and killing the virus.
“A strong antibody response does not mean that the body can better neutralize the pathogen,” Tejeira said.
“COVID-19 in particular is dangerous because a high percentage of patients develop autoantibodies that respond to your own molecules and not the pathogen.”
Tejeira added: “An important aspect of immunity is memory. We want our B cells to remember the pathogen he fought, so that they will activate pathogen-specific antibodies when they encounter it again.”
Will we need booster shots? Does this mean that Canada has to receive 30 million doses every six months?
The spectrum of immunity varies according to the virus. A measles vaccination provides lifelong protection, while a flu vaccine is seasonal and lasts several months.
Although no boost shots are yet available, or even vaccinations are being created for certain variants, development is underway and researchers will begin trials as soon as they are ready.
Tejeira says Canada should ensure booster shots, depending on the circumstances, as more variants emerge with no sign of herd immunity.
“If COVID-19 and its variants are still widespread, vaccine protection will decline within the year and the population’s immunity has not yet been reached, then Canada needs to secure and distribute booster shots,” Tejeira said.
Pfizer says based on their real-world research and evidence, they have not seen any changes in antibody levels that could reduce protection against their doses of the vaccine. But Canada is monitoring the progress of the other vaccine candidates under contract who are still in the development phase and planning to get shots.
“Canada is in talks with vaccine developers regarding plans for early and safe access to booster and variant vaccines when available.” Maddison said.
If the vaccination runs out within the year, Canada may have to secure shots, especially if more variants appear, but as research comes in and people are vaccinated, we will know better over time.
While the explosion of vaccines is slow, experts like Tejeira hope the federal government can speed up the process of accelerating vaccine production infrastructure in Canada so that the country does not have to rely on foreign vaccine production.
“We need to continue to focus our efforts on vaccinating everyone. This will give us a better chance of reducing infections, and therefore the risk of generating new variants against which our existing vaccines cannot protect us,” Tejeira said. added.