Numbers behind breakthrough COVID-19 cases in N.S. show vaccines work: expert

The head of the Canadian Center for Vaccinology says breakthrough COVID-19 cases in Nova Scotia are expected, but more importantly, the small number of cases shows just how effective COVID-19 vaccines are.

Every Friday, the province releases a breakdown that details whether new cases in the past week were among fully vaccinated, partially vaccinated or unvaccinated individuals.

In the latest reporting period, the 110 cases between Oct. 28 and Nov. 3 broke out as follows:

• 34 fully vaccinated individuals (30.9 per cent).
• 7 partially vaccinated individuals (6.4 per cent).
• 69 unvaccinated individuals (62.7 per cent).

As of Friday, 78.8 per cent of Nova Scotians were fully vaccinated against COVID-19.

"By math alone, the fact that the majority of cases are in people who are completely unimmunized ... that's telling you the vaccine is very effective," said Dr. Scott Halperin, the center's director.

The majority of new COVID-19 cases have consistently been in unvaccinated people, despite them making up a much smaller chunk of the population than fully vaccinated people.

Hospitalizations, death stats

From March 15 to Nov. 3, 2021, there were 5,833 COVID-19 cases in Nova Scotia. Almost 87 per cent of those infections have been in unvaccinated people.

Of the 308 people hospitalized, 85.4 per cent of the individuals were unvaccinated.

There have been 35 deaths, 80 per cent of which were among unvaccinated people.

'The virus loves the unvaccinated,' says premier

At Friday's COVID-19 briefing, Premier Tim Houston said the province is focused on getting more and more Nova Scotians fully vaccinated against COVID-19.

"The virus loves the unvaccinated," he said. "That's why we're still focused on getting first and second doses to Nova Scotians."

The unvaccinated cohort includes children under 12 who aren't eligible to be vaccinated yet, although that could change soon. It was announced last month that Pfizer-BioNTech was seeking authorization for its COVID-19 vaccine for use on children five to 11.

"We need to get unimmunized people — including children — immunized, and, hopefully, we'll be able to do that within the next month," said Halperin, who is also a microbiology professor at Dalhousie University in Halifax.

Why breakthrough cases are inevitable

He said it's not surprising there are breakthough cases. The COVID-19 vaccines were designed for SARS-CoV-2, the coronavirus that first swept around the world, whereas variants are the dominant strains in circulation today.

Companies such as Pfizer-BioNTech and Moderna have touted the efficacy of their COVID-19 vaccines at around 95 per cent.

Halperin said we now know vaccine effectiveness wanes a bit over time, but the COVID-19 case numbers show just how effective they are, especially in light of the variants that have higher transmissibility and are deadlier.

He said the only way for there to be no breakthrough cases would be for a virus to not change over time, which is unrealistic.

"We've never achieved that with any vaccine, where there is 100 per cent efficacy," said Halperin.

Overcoming vaccine hesitancy

And for people who remain hesitant about getting a vaccine because they wanted to wait to learn more about potential side effects, Halperin said billions of COVID-19 vaccine doses have been given out worldwide over the past year, and they're safe and effective.

"This vaccine is not so new anymore," he said.

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