‘Breakthrough’ COVID-19 cases: The possibility of infection after vaccination

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    TORONTO, Ontario (CTV Network) — As vaccine rollouts continue to ramp up across much of Canada, experts say there is a chance that some Canadians may become infected with COVID-19 after being fully vaccinated.

University of Manitoba virologist Jason Kindrachuk told CTVNews.ca that these so-called breakthrough infections are an expected part of any vaccination process as vaccines are not 100 per cent effective.

“When we look at people that are vaccinated, there is going to be this contingent of people that do not mount a strong enough response to completely defend themselves against getting infected and or developing disease,” Kindrachuk said in a telephone interview on Tuesday.

Kindrachuk explained that everyone’s bodies react differently to a vaccination and “immunization is not 100 per cent effective.” He said this means that there will be some “outliers” who will test positive for COVID-19 despite being inoculated against the virus.

In fact, these breakthrough infections have already started in Canada.

A long-term care home in British Columbia reported a COVID-19 outbreak last week, despite much of the staff and residents having already been fully vaccinated.

Kindrachuk said this is not uncommon and will likely be seen in other settings across the country.

In the United States, it is unclear when the first breakthrough infection occurred, but they’ve since been reported in various states, including Oregon, Texas, Florida, Hawaii, Minnesota, and South Carolina.

However, Kindrachuk said breakthrough infections are typically mild cases and not a cause for concern.

“Those cases are always the exception and not the norm, and we have to keep our minds on how many infections we’ve seen and in this case, how many immunizations are being administered,” Lindrachuk said.

If a high enough number of Canadians are vaccinated against COVID-19, Kindrachuk explained that a single breakthrough infection is unlikely to lead to a large transmission chain or cause recirculation of the virus as communities will have already established “that buffer of people that actually do have protection.”

“The more people that get vaccinated that are surrounding those [breakthrough infections], the lower chance there is of that virus starting to recirculate through the community and making people sick,” Kindrachuk said.

Infectious disease expert Dr. Abdu Sharkawy told CTVNews.ca that “immunity requires time to become established after vaccination.”

“One is most susceptible in the immediate to short-term period following vaccination… to infection due to incompletely established immunity,” Sharkawy said. He added that the time to establish immunity varies from two to 12 weeks depending on the health status of the person receiving the vaccine.

Despite the possibility of infection after a full vaccination, Sharkawy said breakthrough infections do not mean that vaccines are ineffective or that people shouldn’t get vaccinated.

“The vaccines do protect and do so very well in the vast majority of cases, but it takes our immune system time to mount the adequate response. We need to be mindful of this before we judge a vaccine as ineffective,” he said.

While he acknowledges that the likelihood of breakthrough infections will decline as more of the population is vaccinated, Sharkawy says these cases reinforce why public health measures need to be followed “for the foreseeable future,” especially during the first few weeks following inoculation.

If they’re not followed, Sharkawy said a vaccinated person’s “false sense of security” can create outbreaks that may potentially cause serious disease or death for those who are still unvaccinated or otherwise susceptible.

“This is why masking, distancing, [and] limiting contacts, needs to remain part of the post-vaccine protocol for a while yet,” Sharkawy said.

He says how long public health measures will have to remain in place will largely depend on how much of the community is vaccinated and what level of virus transmission remains.

“The better the situation is for those two critical determinants, the more likely it is that we will be able to engage more safely with one another and not worry as much about breakthrough infections,” Sharkawy said.

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