Low vaccine uptake in pockets of Manitoba hampering goal of herd immunity, top doctor warns

Winnipeg -

Low vaccine uptake in pockets of the Southern Regional Health Authority and the emergence of the more transmissible delta variant could make it more difficult for Manitoba to reach herd immunity, the province’s top doctor warned.

So far, nearly 65 per cent of all Manitobans, (including children under 12 ineligible to receive a vaccine), have been fully immunized against COVID-19.

As of Wednesday, vaccine uptake among those 12 years and older in the Stanley health district sat at just 22 per cent, 38.5 per cent in Winkler and 45.7 per cent in the Hanover health district near Steinbach.

Doctor Brent Roussin, Manitoba’s chief provincial public health officer, said a higher percentage of the population needs to be vaccinated to reach herd immunity while the delta variant is circulating.

“So that means the original projection of people that need to be vaccinated is increased,” Roussin said. “Again, those calculations of herd immunity assume even uptake throughout a population so when you look, we have pockets of low uptake, then it’s very difficult to achieve herd immunity because you’re going to still see transmission in those areas.”

Cynthia Carr, a Winnipeg-based epidemiologist and founder of EPI Research, said to obtain herd immunity a population must reach a critical vaccination threshold. Some experts previously pegged that threshold to be 70 per cent of a total population vaccinated, but Carr said delta has moved the goal posts.

“Basically, right now because of how infectious the delta variant is for example, we’re looking at a critical vaccination threshold of about 85 per cent of the population to reach a goal of herd immunity,” Carr said. “Again the herd immunity concept is the more of us that are protected that can’t spread virus…even if it does spread a little bit amongst people who are fully-vaccinated, for the most part we are protected against the most severe health outcomes.”

Individuals who develop immunity through natural infection only make up a small component of herd immunity, but it is not a goal to get infected and it is not enough to protect yourself and others, Carr warned.

“Your natural immunity will vary depending on the level of virus that you had, how your body reacted to that,” she said. “So again, that is not enough but there will be a component of the population that has some natural immunity and ideally those people are also vaccinated for the best possible protection.”

Carr said the critical vaccination threshold is based on a mathematical formula which takes into account two important factors: how effective the vaccine is at stopping the spread of infections and how infectious the virus is.

“As the ability of that virus changes in terms of the number of people it can infect, even if everything else stays the same, that critical vaccination threshold increases,” Carr said. “It could’ve been 75 per cent against the original version of the virus because it could infect about two to three other people. Now with delta, where the estimates are six to eight other people infected, that critical vaccination threshold goes up to somewhere 85 per cent and over at this point.”

DATA SHOWS VACCINE EFFICACY

The latest COVID-19 infection numbers released by the province highlight the effectiveness of vaccines. Of 105 new cases identified Wednesday, 70 were in people who were not fully vaccinated, including 41 cases from the Southern health region – an area which accounted for the majority of new cases identified.

Officials have said those not yet vaccinated are more likely to spread the virus and experience severe outcomes than those who are fully vaccinated.

On Tuesday, Manitoba announced a requirement for provincial employees who work with vulnerable populations – doctors, nurses, teachers and child care workers – to be fully immunized against COVID-19 by Oct. 31 or undergo regular testing.

The province is also planning to expand the list of services, activities and places that only fully vaccinated people can attend.

TARGETING VACCINE HESTIANCY

Martin Harder, the mayor of Winkler where uptake remains low, isn’t convinced the new measures will incentivize vaccination. He thinks it will have the reverse effect on people who have yet to be vaccinated.

“I still think we’re having an opportunity here to be able to be vaccinated to prevent some of the seriousness of the delta variant. Yet at the same time, when you have the restrictions and the hammer come down placed on people within the community, I think the resistance strengthens,” Harder said.

He sees testimonials from people about the effectiveness of vaccines as a better way to encourage people to get their shots.

“I think we haven’t done a good enough job talking about the benefits and acknowledging the fact that some people who have been vaccinated are still subject to a degree of impact but yet if that degree is less severe, then we should talk about those,” Harder said.

Carr feels it would be unfortunate if people doubled down due to new mask and vaccination mandates coming into force in Manitoba, but she understands people have legitimate questions and concerns about vaccines.

“There are no stupid questions,” Carr said. “What we don’t want is this continued escalation of myths and complete falsehoods that is scaring people and motivating people to put their lives at risk, literally, to not get vaccinated.”

She warned if groups of people remain unvaccinated, it will not only hamper the province’s ability to reach the critical vaccination threshold, it could also result in the emergence of new variants.

“Let’s help other people get vaccinated, not attack them, not shame them.”