TORONTO -- With the approval of the one-shot vaccine from Johnson & Johnson, Canadians now have four COVID-19 vaccine options that have been tested by researchers and carefully scrutinized by regulators.

The vaccines are considered safe, but even pharmaceuticals approved for widespread use are sometimes not appropriate for people with certain allergies or other medical conditions. However, experts consulted by say there are very few situations where not taking the vaccine would be the better option. 


With vaccines – as with other pharmaceuticals – there is always a chance of a minor adverse reaction, such as minor pain or swelling at the injection site. But there is also a small risk of a more severe anaphylactic reaction to an ingredient, such as to polyethylene glycol (PEG), which is present in the Moderna and Pfizer vaccines. 

“If you had a known allergic reaction to something like that then I think it's reasonable to consult with someone before you go ahead and get vaccinated. But most people with milder allergies, I wouldn't be concerned at all,” Dr. Matthew Muller, Medical Director of Infection Prevention and Control at St. Michael’s Hospital, and Ontario lead for the CANVAS COVID-19 vaccine project, told

According to Health Canada, out of nearly 1.8 million vaccine doses administered as of Feb. 26, there were just under 50 anaphylactic reactions, or 0.0028%. 

It is still possible those with allergies to specific ingredients may still be able to receive a vaccine, but this should be done in a closely monitored situation and after discussion with a physician, said Muller.

One of the more common vaccine allergies relates to eggs, which are sometimes used in vaccine production. However, none of the four Health Canada-approved vaccines were made using eggs.


People with compromised immune systems are often wary of vaccines out of concern it could replicate and given them the disease they’re trying to prevent. However, none of the four COVID-19 vaccines in Canada are made with ‘live’ virus in them.

“These are not live vaccines, they're not replicating at all. So if you have been cautioned before about live vaccines these are not them,” says Dr. Omar Khan, a professor of Biomedical Engineering at University of Toronto. “In general, for people who have weakened immune systems, a vaccine is actually a really great way to get antibodies.”

If there is any reason for immunocompromised people to worry, it’s that the vaccines may have reduced efficacy, although there’s currently not enough data to be conclusive. 

Another issue that has been a point of worry for some is whether the vaccines are safe for people with a history Guillain-Barré syndrome (GBS), which is a rare disorder where the body’s immune system essentially attacks the nervous system, sometimes causing paralysis.

There have been links in the past between GBS and certain flu vaccines, and some doctors recommend taking precautions with a flu vaccine for people with a history of GBS. 

However, studies on the issue have been inconclusive, and as the COVID-19 vaccines are completely different from flu vaccines, there’s no reason to think there is a link, says Muller.


Regulators have so far avoided making a call on COVID-19 vaccine safety for pregnant or lactating women, but that is only because of a lack of data, says Khan.

“None of the clinical trials have looked at that subset of the population,” he said. “It’s not because it's dangerous but because you never want to recommend something without the hard data to back it up.” 

Currently, Canada’s National Advisory Committee on Immunization (NACI) recommends vaccines can be offered to pregnant or lactating women based on an individual risk assessment.


There are no additional risks for people who have already contracted COVID-19, and indeed those who have recovered may have some level of immunity, but it is not clear how much.

“Some people assume they don't need the vaccine, but right now we are recommending that people who have had COVID should be vaccinated. Especially those that may have had a mild case, we don't know if you amount to sufficient immune response,” says Muller.

Both Muller and Khan say that anyone with concerns about whether they may have a risk factor associated with a vaccine should consult their own doctor for answers. And in the vast majority of cases, any risks of receiving the vaccine are outweighed by the risk of contracting COVID-19 itself.