Infectious disease expert says B.C. needs to be more transparent with breakthrough COVID-19 cases

A B.C. infectious disease expert says the province should release more detailed information about who among the fully vaccinated is contracting breakthrough COVID-19 infections.

Dr. Brian Conway of the Vancouver Infectious Disease Centre says the majority of breakthrough cases result in mild symptoms, but understanding who is most at risk will better target interventions to stem the spread of the disease.

"What we are doing right now isn't working as well as we would like," Conway said. "Let's try and prioritize who ... are getting these breakthrough infections so we can focus our booster program on those individuals."

In a statement, the Ministry of Health said its main focus is vaccine effectiveness.

"BCCDC does not have information about whether the cases are immunocompromised or had underlying health conditions," they said.

A new study out of the U.K. is shedding light on where breakthrough cases are occurring.

Researchers from the University of Oxford recently published a paper ranking those in the U.K. most at risk of breakthrough infections and who are at higher risk of being hospitalized or dying from infection.

The data, collected from around five million fully vaccinated people, shows that only a small minority remain at risk of COVID-19 hospitalization or death. But some key risk factors include: living with Down's syndrome, sickle cell disease, HIV, AIDS, dementia, Parkinson's disease, neurological conditions, or liver cirrhosis, being a recipient of a kidney, bone marrow or solid organ transplant; undergoing chemotherapy and living in a care home.

Thousands of people who are immunocompromised are eligible for a third dose of COVID-19 vaccine in B.C., including those who have had a solid organ transplant, a bone marrow or stem cell transplant, have combined immune deficiencies, among other immunological conditions. 

As of Oct. 4, British Columbians living in long-term care and assisted living homes will also start receiving COVID-19 booster shots.

Increase in breakthrough cases

The province's data shows an increase in breakthrough cases where an infection occurred at least two weeks after a second dose.

The data shows that of the people who contracted COVID between Sept. 22 and 28, 28.8 per cent were fully vaccinated.

That's compared to the Aug. 23 - 29 reporting period, where 19.8 per cent of infections were among fully vaccinated people.

Dr. Maryam Zeineddin, a family physician in West Vancouver, said there was a spike in cases over the last couple of days, but the Vancouver Coastal Health region has been protected by high immunization rates. More than 80 per cent of eligible British Columbians have received both doses of the vaccine.

"As long as all of us are vaccinated ... it really decreases the danger of this virus," she said.

Despite current health orders for most of the province placing no restrictions on personal gatherings, Conway says he still has concerns about the potential risks of people gathering over the upcoming Thanksgiving Day long weekend.

"They'll want to get together with a large number of people and they'll say 'it's almost over and doing it for one night won't hurt.' It's not almost over and one night might hurt," he said.

"Too many people are thinking that COVID is about to come to an end  … and that's just simply not the case."

During a news conference on Oct. 1, Dr. Bonnie Henry reminded British Columbians that some regions, namely Interior Health and eastern Fraser Health, currently restrict gathering sizes and those rules must be followed as we head into the Thanksgiving weekend. She also said it's important for any elderly family members to be fully vaccinated if they plan to gather with loved ones for the holiday.

Zeineddin recommends those gathering for Thanksgiving, even people who are fully vaccinated, continue to practise handwashing and physical distancing to minimize transmission. 

"The Delta [variant] is a much more aggressive variant of COVID," she said. 

The province's most recent modelling shows two doses of any vaccine to be highly protective, including against the Delta variant.

The data shows hospitalization risk is reduced by 90 per cent, and infection risk reduced by 90 per cent for recipients of mRNA vaccines such as Pfizer-BioNTech or Comirnaty, 70 per cent for recipients of viral vector-based vaccines such as AstraZeneca or Vaxzevria, while mixed doses "offer protection similar to two mRNA doses."

Conway says emerging data shows booster shots will likely be required six months after people get their second dose, but adds that the vaccine alone isn't going to lead the province toward community-based immunity.

"Understanding where the breakthrough infections are occurring will help the people of British Columbia, the people of Canada and public health officials target our interventions better."