TORONTO -- Experts say COVID-19 vaccines may promote little or no response in people taking certain medications or those with underlying conditions, and are calling for more research to protect this group.
Dr. Deepali Kumar, the head of the University Health Network's Transplant Infectious Diseases Clinic in Toronto, told CTVNews.ca that researchers don't yet know how effective COVID-19 vaccines are in immunocompromised patients.
"We know that in immunosuppressed people, antibody responses are generally lower for COVID vaccines than in the general population… but we don't know how well the antibody responses translate into effectiveness, so actually preventing COVID disease in immunosuppressive people," Kumar said in a telephone interview on Thursday.
Someone is considered immunocompromised if they have a medical condition that weakens their immune system, including cancer and organ transplants, or are taking medications that reduce their ability to fight infection, such as anti-rejection drugs and steroids.
Because of this, experts say, the COVID-19 vaccines may have reduced efficacy in immunocompromised individuals, although there is currently not enough data to be conclusive.
A study published Thursday found that nearly three per cent of American adults under age 65 take medications that weaken their immune systems and may limit their response to the COVID-19 vaccine.
"We're starting to realize that people taking immunosuppressive drugs may have a slower, weaker response to COVID vaccination, and, in some cases, might not respond at all," Beth Wallace, a rheumatologist at Michigan Medicine and lead author of the study, said in a .
"We don’t have a full picture on how these drugs affect the vaccine’s effectiveness, so it’s difficult to formulate guidelines around vaccinating these patients," she added.
COVID-19 vaccine makers excluded immunocompromised people from their clinical trials and as a result, there is limited information about how this group is reacting to the shots.
RESEARCH IN THE WORKS
A study found that 46 per cent of 658 transplant patients studied did not mount an antibody response after the two-dose series of the Pfizer-BioNTech or Moderna COVID-19 vaccines.
"Although this study demonstrates an improvement in … antibody responses in transplant recipients after dose two … these data suggest that a substantial proportion of transplant recipients likely remain at risk for COVID-19 after two doses of mRNA vaccine," the study read.
The researchers found that this lack of a reaction is likely a result of the immunosuppressive drugs transplant recipients take.
"We know from other vaccines that steroids, as well as anti-rejection treatments and cancer chemo therapies, do impact vaccine efficacy and make it lower," Kumar said.
A study conducted by researchers out of Washington University reported that the majority of patients with autoimmune conditions studied mounted an antibody response to the COVID-19, but about 15 per cent did not.
The participants in the study had a range of medical conditions that supressed their immune system, including inflammatory bowel disease, systemic lupus and rheumatoid arthritis.
The researchers noted that those who were most affected were on B-cell-depleting medications, such as those for cancer, multiple sclerosis, and rheumatoid arthritis.
The Washington .
While the U.S. Centers for Disease Control and Prevention acknowledges that immune-suppressed people might not be as protected as other fully vaccinated people, there are no set recommendations for what precautions they should take.
Kumar recommends these people try "as much as possible" to time their COVID-19 vaccinations around their immune suppression.
"So get the vaccine when you’re on the lowest immunosuppression possible," Kumar said. "For example, in the transplant patients we recommend that they actually get their vaccine before they get their transplant and get on anti-rejection drugs."
If they’ve missed that opportunity, Kumar suggests waiting one to three months before being vaccinated, but said the decision should ultimately be discussed with the patient and their physician.
ADDRESSING IMMUNITY
Despite there being limited data on the efficacy of the vaccines, experts say immunocompromised individuals should still get the jab.
People with compromised immune systems are often wary of vaccines out of concern they could replicate and give them the disease they are trying to prevent.
However, Omar Khan, an assistant professor of biomedical engineering at University of Toronto previously told CTVNews.ca that 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," Khan said. "In general, for people who have weakened immune systems, a vaccine is actually a really great way to get antibodies."
Health experts are currently debating what to do to . Kumar says one or more booster shots may be needed for those with weaker immune response.
She noted that researchers out of the Toronto-based University Heath Network are currently studying the effects of a third COVID-19 vaccine dose in immunocompromised patients, specifically in transplant recipients.
"What we're hoping is that with a third dose, we can increase antibodies to just as high as an immune competent person who has gotten two doses," Kumar said.
In addition, she said, there should be more research into whether certain types of COVID-19 vaccines work better in those with autoimmune disorders than others.
Kumar said immunizing those around this group, such as family and friends, can help protect them, in addition to continuing to follow public health measures, including hand washing, physical distancing and masking, until more of the population is fully vaccinated.
"People really need to continue to practise good public health measures… and that's because we don't know who in the population has developed an adequate immune response," Kumar said.
"I don't think there's any good measure right now of who is going to be protected or not. We have antibodies, but we don't know at which level of antibody you're protected," she added.
