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What you need to know about the bivalent booster shots

The new bivalent booster will be available for all adults across the country by the end of this month. Have some questions? Check out our FAQ for what you need to know.

We’ve answered some of your questions about the new vaccine

A man with a mask and blue gloves holds a syringe in his hand.
A coronavirus vaccine is prepared at a clinic in Vancouver earlier this year. The bivalent booster shots are now available to adults across provinces in Canada. (Ben Nelms/CBC)

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Appointments to get the new bivalent booster shots have opened up across provinces in Canada for all adults. 

The vaccine was initially available for provinces' more vulnerable populations at the beginning of September, but has since been made available to everyone over the age of 18. 

Health officials have noted the importance of getting the shot, especially as the colder months approach, but the timing may vary person-to-person, based on when you were last infected or last vaccinated.

We've also received a number of questions about the bivalent booster and are here to answer them. 

What is a bivalent COVID-19 vaccine? 

Simply put, a "bivalent" vaccine is a type of vaccine that protects against a combination of two or more coronavirus strains.

This helps to create a broader immune response and improves the strength and duration of protection against the most dominant COVID-19 variants in circulation.

What about bivalent boosters for the BA.4 and BA.5 Omicron strains?

Health Canada recently approved an updated Pfizer-BioNTech Comirnaty COVID-19 vaccine targeting the dominant circulating Omicron subvariants BA.4 and BA.5, as well as the original strain of the virus.

Moderna's updated vaccine, Spikevax, which was approved in September, is different in that it targets only the original strain and the BA.1 Omicron subvariant. Health Canada says clinical trials suggest Moderna's bivalent booster elicits a "stronger immune response" against the more recent mutations of Omicron — BA.4 and BA.5 — than the original Moderna vaccine.

Both the Moderna and Pfizer-BioNTech bivalent shots are expected to offer better protection against the circulating Omicron strains.

Moderna's application for a second bivalent booster that targets BA. 4 and BA. 5 was received by Health Canada on Sept. 12, 2022 and is currently under review.

How is it different from the previous vaccines?

The bivalent vaccines contain two messenger RNA (mRNA) components instead of one. 

One of the components is from the original strain of the coronavirus, while the other component is from the Omicron strain, according to the U.S. Food and Drug Administration (FDA). However, it is only approved for use as a booster dose. 

A vial of vaccine.
The Ontario government announced the rollout of bivalent booster doses early Monday morning. (Rogelio V. Solis/The Associated Press)

In general, "bivalent" or combination vaccines are very common. According to B.C.'s public health website, the most common is the influenza vaccine, which protects against three to four strains of influenza.

The effectiveness of the vaccine mainly depends on when you received your last booster or last had a COVID-19 infection. 

What happens to the older vaccines?

Because the bivalent vaccines are distributed as a booster shot, the older vaccines are still required as the primary series. 

According to the latest data, there are still thousands of Canadians who have not received the first two shots, and since those shots are the only ones currently approved for the primary series, Canada is going to hold on to those doses. 

However, a recent agreement between the federal government and Moderna will allow for six million of the company's original vaccines to be converted to the Omicron-containing bivalent boosters.

Many vaccines have expired since they first became available. Around nine million doses in the federal stockpile reached their expiration date and were disposed of, a Public Health Agency of Canada spokesperson said

When should you get it?

While there has been some debate about the right time to get the bivalent booster, experts agree it should be administered between three to six months since your last booster or last COVID-19 infection.

"If you're an individual who is living in a high-risk area or has comorbidities and you feel that you want to inch towards the three-month mark, have a consultation with your primary care physician or reach out to your public health unit," said Dr. Nitin Mohan, a physician and epidemiologist in Ontario. 

If you think you may be at risk for more severe illness, or aren't entirely sure, you can refer to this guide published by the federal government

Experts also recommend the same time frame if you have recently recovered from a COVID-19 infection. 

"Because you [get] a boost of antibodies from the COVID-19 infection, you want to give it time for those to fall for the booster to have a maximum effect," explained Dr. Christopher Labos, epidemiologist and cardiologist in Quebec.

The important thing to remember is that you need the initial two-dose series before you can get the bivalent booster.

Is it beneficial to hold off getting your yearly flu shot?

Whether you want to get the bivalent booster and the flu shot at the same time, or during separate appointments is entirely up to you.

At the beginning of the pandemic, medical experts recommended against getting both shots at the same time due to possible confusion on which vaccine was causing potential side effects.

WATCH | Infectious disease expert answers questions about Moderna's new bivalent booster: 

Should you get Moderna’s bivalent COVID-19 vaccine?

3 months ago
Duration 4:11
Infectious disease expert Matthew Miller answers questions about Moderna’s new bivalent COVID-19 vaccine, which targets the Omicron variant, and when people should get it.

"I think we have enough experience with the COVID-19 vaccine that we know the side effects are mostly going to be mild," said Labos, noting "it doesn't really make much of a difference" if you get them together or separately. 

As for side effects — those experiences are typically specific to each person, but Labos says it's safe to expect an experience similar to your previous shots.

"Whatever happened to you before will probably happen to you again."

Where can I get it and who is eligible?

That depends on where you live.

Each province and territory has its own eligibility criteria and recommendations on the waiting period before you can receive a bivalent booster shot.

The National Advisory Committee on Immunization (NACI) recommends that the updated vaccine be offered to adults who are recommended to receive a fall booster dose.

Also, adolescents between 12 and 17 with "moderately to severely immunocompromising conditions" and those who have elevated social risk factors could be offered the vaccine, according to NACI.

Here's where you can find the eligibility criteria for a bivalent booster shot and where it is provided in every province and territory as of Sept. 27, 2022:


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