C/O Daniel Schludi

Immunocompromised populations can now receive the third dose of the COVID-19 vaccine in Ontario

By: Anna Samson, Contributor

On Sept. 10, the National Advisory Committee on Immunization released new guidelines regarding the third dose of the COVID-19 vaccine to now include immunocompromised people. Based on this recommendation, Chief Medical Officer, Dr. Theresa Tam has advised that immunocompromised individuals should receive a third dose of the vaccine to build a stronger immune response to the COVID-19 virus. Eligible individuals will be contacted by their doctors and given a referral form for the third dose. This additional dose of the COVID-19 vaccine can be administered a minimum of eight weeks after receiving the second dose.

The decision to include immunocompromised people for third dose eligibility supplements the previous month’s announcement to add a third shot to Ontario’s one or two dose vaccine series rollout plan. However, the third dose is only available for specific vulnerable populations. Previously, the vulnerable groups eligible for the third vaccine dose consisted of transplant recipients, those with hematological cancers undergoing active treatment, recipients of an anti-CD20 agent and those in high-risk settings such as long-term care homes and First Nations elder care lodges.

Now, immunocompromised individuals are added to the list. This includes those undergoing active treatment for solid tumors, those in receipt of chimeric antigen receptor (CAR)-T-cell, those with moderate or severe primary immunodeficiency, Stage 3 or advanced untreated HIV infection and those with acquired immunodeficiency syndrome and those undergoing active treatment with immunosuppressive therapies.

For the general population, receiving the recommended one or two doses of the vaccine offers sufficient protection against the COVID-19 virus and its variants, including the highly transmissible Delta variant. However, immunocompromised individuals have a lowered immune response to the recommended one or two dose vaccines and require a third dose to build up adequate immunity.

Matthew Miller, a member of The Michael G. DeGroote Institute for Infectious Disease Research, the McMaster Immunology Research Centre and the National Advisory Committee on Immunization, reiterated this. 

“We actually consider this third dose a way for them to complete their primary immunization series and the reason for that is because the immunocompromised people and some frail elderly people like those who live in long-term care settings just don’t mount as good of an immune response as the general population,” said Miller. 

Miller went on to explain how a third dose for immunocompromised people is equivalent to the two doses that others receive. 

“[B]y giving them a third dose, what we’re trying to do is just get them to the same level that everyone else is at after two doses. It’s not that we’re really boosting them, it’s just we’re trying to get them up to the same point as everyone else because of the way that their immune systems [respond] more poorly to vaccines in general,” said Miller. 

There are fewer COVID-19 antibodies in fully vaccinated immunocompromised people than in fully vaccinated non-compromised people. These antibodies also wane faster in vulnerable populations as compared to the general population. Immunocompromised people are more likely to be adequately equipped against the COVID-19 virus when they have received a third dose of the vaccine to assist their immune response.

Following the provincial guidelines, Hamilton is now offering immunocompromised residents a third dose of the vaccine. The additional dose can be received at any Hamilton Public Health Services’ community clinics, St. Joseph Healthcare Hamilton and most pharmacies. To receive the third dose, individuals must bring a completed referral form given to them by their doctors. 

According to Miller, additional vaccine doses are not available on the McMaster University campus because a third dose is administered after verification from a physician.

“[T]hose additional doses are normally procured after talking to a physician who knows your medical history and if you fall into one of those [eligible] categories,” said Miller.

The pandemic has been especially difficult for immunocompromised people and other vulnerable populations at a higher risk of infection. Many of whom have had to be extra vigilant to protect their health during the last year and a half. Receiving a third dose of the vaccine offers a better chance for these vulnerable groups to armour themselves against COVID-19.

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