Interpreting breakthrough COVID-19 cases in Manitoba

Winnipeg -

As Manitoba continues to grapple with rising COVID-19 case numbers amid the fourth wave, vaccine task force lead Dr. Joss Reimer said Manitobans should not make too much of the uptick in breakthrough cases.

Of the province’s 132 new cases announced Thursday, 37 were fully vaccinated.

Of Wednesday’s 95 new cases, 23 were fully vaccinated Manitobans and on Tuesday, 45 of the province’s 102 new cases were in fully vaccinated people.

Reimer said there are a couple of reasons not to be alarmed at the number of breakthrough cases reported each day.

“The first is that in Manitoba, most of us are fully vaccinated, and so the more of us who are fully vaccinated, the more of us who will be part of the breakthrough cases,” Reimer told CTV News.

“So for example, if 100 per cent of Manitobans were fully vaccinated, then 100 per cent of our cases would be in fully vaccinated people.”

Reimer said this larger pool of fully vaccinated Manitobans makes the numbers tricky to interpret. However, she said the biggest takeaway from the daily data is how many fully vaccinated people who contract the virus avoided hospitalization and severe outcomes.

“Almost all of them are very mild, so we get very few people who are fully vaccinated ending up in the hospital, and almost none in the ICU,” she said.

“There’s really only been a handful of people who after being fully vaccinated, got sick enough that they needed ICU care, and even then, it was shorter stays, they had lots of other major health concerns that made the vaccine less effective for them.”

Saint Boniface Hospital Medical Microbiologist Doctor Philippe Lagacé-Wiens agrees breakthrough cases in the fully vaccinated are to be expected.

“Nothing to be surprised about and it actually corresponds well to the degree of protection that we expected in the vaccinated population,” he said.

“We know the vaccine is somewhere between 85 and 90 per cent effective. It’s simply a rule of mathematics that if you’ve got a much bigger population that is vaccinated, you eventually get close to parity between the cases in vaxxed and the cases in the unvaxxed."

Lagacé-Wiens said it’s reasonable to have group gatherings adhering to public health guidelines where everyone is vaccinated because the risk is very low. However, he says that might change as more cases emerge in the community during the fourth wave.

He added the risk is more complex when adding even one unvaccinated person to a group gathering.

“It's easy enough to say ‘only Uncle Joe is unvaccinated and that is only one person out of 20, I think it’s fine.’ Uncle Joe could very well be a problem if he's infected and then causes breakthrough infections in that group,” Lagacé-Wiens said.