Nova Scotia

N.S. data on 'breakthrough cases' proves COVID-19 vaccines are working, expert says

Initial data provided on Friday shows that people who received one dose of the vaccine made up less than five per cent of the overall cases during Nova Scotia's third wave. People who had received both doses made up less than one per cent. 

People with 2 vaccine doses made up less than 1% of new cases during spring surge

Noni MacDonald, a professor of pediatric infectious diseases at Dalhousie University, specializes in vaccine research. She says initial data on breakthrough cases proves that COVID-19 vaccines are working. (Dalhousie University)

Initial data on "breakthrough cases" proves that COVID-19 vaccines are working in Nova Scotia, according to a researcher at Dalhousie University.

People are considered a breakthrough case when they become infected with the virus more than 14 days after receiving one or two doses of the vaccine.

On Friday, Nova Scotia announced it will start reporting those case numbers each week.

Information provided on Friday shows that people who received one vaccine dose made up less than five per cent of the overall cases during Nova Scotia's third wave. 

People who had received both doses made up less than one per cent. 

Initial data about breakthrough cases shows that people who received one dose of the vaccine made up less than five per cent of the overall cases during Nova Scotia's third wave. (Robert Short/CBC)

"We're looking at real-time vaccine effectiveness," said Noni MacDonald, a professor of pediatric infectious diseases, who specializes in vaccine research.

"Overall, I was very impressed by what the numbers already showed us. These vaccines are really working."

Dr. Robert Strang, the province's chief medical officer of health, explained the breakthrough case data at the COVID-19 briefing on Friday.

Between March 15 and June 1, there have been 3,902 COVID-19 cases. Of those:

  • 3,691 (94.6 per cent) were unvaccinated.
  • 187 (4.8 per cent) were partially vaccinated.
  • 24 (0.6 per cent) were fully vaccinated.

Of the 242 individuals who were hospitalized:

  • 214 (88.4 per cent) were unvaccinated.
  • 26 (10.7 per cent) were partially vaccinated.
  • Two (0.8 per cent) were fully vaccinated.

Of the 19 individuals who died:

  • 16 (84.2 per cent) were unvaccinated.
  • Two (10.5 per cent) were partially vaccinated.
  • One (5.3 per cent) was fully vaccinated.
Dr. Robert Strang, Nova Scotia's chief medical officer of health, said some people may be more susceptible to COVID-19 even if they've been immunized. (Communications Nova Scotia)

Strang reminded Nova Scotians that breakthrough cases will happen because no vaccine is 100 per cent effective.

"The vast majority of people get good protection from the vaccine. But there are some who don't get as good protection, especially older people and people with underlying immune conditions," he said at the briefing.

"That's one of the key reasons why we have to have high levels of uptake in the overall population, to protect those around us who may not individually respond as well to the vaccine."

MacDonald said people are eager to understand the effectiveness of the vaccines, and it's important to inform the public about the breakthrough cases.

"I am simply delighted that they're doing this," she said. "This is part of truth-telling. You don't want to hide information. You want the general public to understand [and] expect it to come."

She said this transparency may help people who are vaccine hesitant.

"[We need to] make sure we say this in a way that they can hear it loudly, at how effective these vaccines are," she said

Effectiveness against variants unknown

MacDonald said although this new data is helpful, it doesn't reveal if any of the breakthrough cases were COVID-19 variants.

Studies have shown that vaccines may be less effective against more transmissible and harmful variants. One of those is almost entirely to blame for Nova Scotia's third wave.

By comparing the variant data and breakthrough cases, MacDonald said the province would be able to determine if the vaccines have been effective against the variants.

"As we go forward and more variants are going to be out there around the world, having this system in place and being able to follow this will really help us look at how effective our two doses of this vaccine [are] in our very own country," she said.

MacDonald said she's hopeful the rest of the country will follow Nova Scotia's lead and start providing regular updates about vaccine efficacy as more people are immunized.

With files from Kayla Hounsell

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