COVID-19 vaccine recall: how long to wait?

Amid the rapid increase in the Omicron variant in Canada, health officials are urging Canadians to receive their third dose of a COVID-19 vaccine for better protection.

But provinces and territories have different eligibility timelines, so when exactly should Canadians be aiming for their third jab?

“After six months of your second dose, you should receive your booster, especially if you are … over 50 and considered to be at risk for serious illness,” Research Institute scientist Angela Crawley told CTVNews. from The Ottawa Hospital. .ca Tuesday during a phone interview.

Crawley is referring to the latest booster dose guidelines released by the National Advisory Committee on Immunization (NACI) on December 3. The committee strongly recommends that several populations receive the third dose of the COVID-19 vaccine at least six months after receiving their second dose. Third doses “may be offered” to Canadians aged 18 to 49 as well, depending on where they live and individual risks, according to NACI.

At this time, only the mRNA vaccines – Pfizer-BioNTech Comirnaty and Moderna Spikevax – have been approved for third dose use. In both cases, Health Canada authorized the use of these vaccines at least six months after a person completed their primary course.

Despite recommendations to wait at least six months, several Canadian provinces have set third-dose eligibility requirements that do not force residents to wait that long. In Alberta, for example, people 18 years of age and older can reserve their booster dose only five months after receiving their second dose. In provinces like Saskatchewan and Ontario, the interval is even shorter, at just three months.

“I think it’s confusing for Canadians for sure,” University of Saskatchewan epidemiologist Dr. Nazeem Muhajarine told CTVNews.ca on Tuesday in a telephone interview. “It seems to be the fluke of the residency … determining if you can get a booster dose.” “

Muhajarine and Dr. Peter Juni, head of the Ontario Scientific Advisory Table on COVID-19, are asking provinces that currently require residents to wait at least six months to opt for shorter intervals, due to the emergence and high transmissibility of Omicron.

“Everything has changed with Omicron, there are new rules of the game,” Juni told CTVNews.ca Tuesday in a telephone interview. “What was still relevant six weeks ago is now obsolete.”

Juni pointed to recent data from the UK suggesting that protection against COVID-19 infection wanes after about three months after receiving the second dose of the Pfizer vaccine. According to Juni, this data is likely valid for those who also received a second dose of Moderna. In late November, the UK government announced that all adults would be eligible to receive their third dose of a COVID-19 vaccine after just three months after receiving their second dose.

Muhajarine pointed to another study in Israel, demonstrating the effectiveness of a third dose of Pfizer vaccine in reducing the risk of hospitalization and death from the disease. Study participants were vaccinated at least five months after receiving their second dose. Israel also recently announced that it would reduce the time lag between offering the second and third dose of the COVID-19 vaccine to three months, from five months previously.

“The data we’re seeing really indicates a much shorter interval as the optimal interval to deliver a third dose,” he said. “I think six months might be the real outer limit of that.”

As residents across the country face recall eligibility requirements based on their province or territory of residence, Muhajarine said he always encouraged those who received their second dose of the COVID-19 vaccine ago. has at least three to five months to get the booster dose as quickly as possible.

“We are facing a variant that is really effective in evading vaccine-induced antibody immunity,” he said. “When the third dose … is in place, our immune response is restored and is able to continue to protect [against] serious illness.

WEAK PROTECTION AGAINST INFECTIONS AFTER TWO DOSES

With a second-dose rollout that took place across the country over the spring and summer months, Juni said most Canadians are now more than three months after completing their primary vaccine series.

Looking at preliminary data recently compiled by the province’s Science Table, it appears that two doses of current COVID-19 vaccines offer relatively good protection against hospitalization and ICU admission, Juni said. The province, however, has seen a rapid decline in protection against infection since the emergence of Omicron.

“People who have received two doses and are more than three months after their second dose really have to behave as if they are unvaccinated when it comes to their risk of infection,” he said. “Vaccine protection against infection is declining to almost zero now. “

While this data is based on what Ontario is experiencing, Juni said other provinces will likely see the same.

“To suggest that it won’t is like suggesting to the province that gravity doesn’t apply; it will be, ”he said.

In British Columbia, all adults in the province recently became eligible to receive their third dose of the COVID-19 vaccine at least six months after receiving their second dose. While the Omicron cases recorded in British Columbia so far are not as high as those recorded in Ontario or Quebec, the protection offered by the third doses is crucial to reducing the severity of the COVID infection. 19, said Muhajarine.

“Across the country, transmission is high … every province is experiencing outbreaks caused by Omicron,” he said. “The booster doses are what will protect those infected from severe COVID-19 which will require hospitalization and the use of an intensive care bed. “

THIRD DOSES AND PUBLIC HEALTH MEASURES NECESSARY TO COMBAT THE FIFTH WAVE

This is why the third doses of the COVID-19 vaccine are so important, explained Juni, especially for the most vulnerable, including those who are older or have underlying health conditions. Still, the epidemiologist said he recognized that it took more than vaccines to stop the fifth wave.

“Efficiency [of current vaccines] is not as perfect as for Delta, but it’s good, ”he said. “But at the moment, that’s far not enough. We need the combination of an aggressive recall deployment with public health measures. “

In addition to making an appointment for a third jab, Juni advises people to stay put and reduce contact with others as much as possible. This includes avoiding crowded indoor spaces such as bars and restaurants. He also recommends wearing a medical mask topped with a two-layer fabric mask for the perfect fit and extra protection.

Crawley is also strengthening general COVID-19 public health measures such as the practice of physical distancing and hand hygiene. It also indicates other ways to maintain general well-being, such as getting a good night’s sleep, staying hydrated throughout the day, and eating a balanced diet.

Apart from that, Muhajarine and Juni said they hoped to see provinces update their third-dose eligibility requirements to reflect a three-month gap between the second and third dose of vaccine to offer a additional protection to residents earlier.

“The challenge we have is that these infections are so pervasive, so prevalent in the population,” Juni said. “Policies have to change. “

About John McTaggart

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