Modelling group says B.C.'s under-reporting of COVID-19 data makes personal risk assessment harder

An independent modelling group says that B.C. is under-reporting all major COVID-19 metrics, making it impossible for residents to know their true risk.

According to a report published last week by the B.C. COVID-19 Modelling Group, blood sample data shows that the number of new cases could be under-reported by as much as 100 times.

The group, which consists of experts from the University of British Columbia, Simon Fraser University and the University of Victoria, also says that population-level immunity to the virus is waning.

Sarah Otto, one of the co-authors of the report, says that the province was still at a "high level" of infections and hospitalizations.

"I think that's going to get worse unless people really ratchet up their protections," she said. 

"Including getting vaccinated, but doing as much as they can to minimize risks, by interacting in well-ventilated spaces and with masks on."

Infections could be 100 times higher

The report uses two data sets — one of which was in a study co-authored by B.C. Provincial Health Officer Dr. Bonnie Henry — to estimate how drastically cases are being under-reported.

All cases reported weekly by the B.C. Centre for Disease Control (BCCDC) are PCR tests, which are currently inaccessible to the majority of British Columbians.

The two data sets used blood samples to estimate the levels of COVID-19 antibodies in a population. The report says that the data shows the under-reporting of cases in B.C. is approximately 100-fold.

The highly infectious BA.5 Omicron variant is currently dominant in the province, according to the report, with more sub-variants on the way that could be even more immune evasive.

Official B.C. statistics show that 365 people were in hospital with the virus Thursday, and 25 new deaths were reported among people who tested positive for the coronavirus within the previous 30 days.

Otto says there's more to the data, now released weekly, than appears at first glance.

She says that unsuspecting members of the public could look at the B.C. Centre for Disease Control's weekly reports and be misled by numbers that will often be drastically revised by the following week.

B.C. shifted in April to reporting key COVID-19 metrics, including cases, hospitalizations, and deaths, once every week. The stats were previously posted daily.

At the time, the province said the move was part of "a shift away from a 'case-management' model to a 'surveillance' approach that focuses on identifying meaningful changes in COVID-19 trends", similar to how the flu is monitored.

However, since weekly reporting was implemented, hospital admissions and deaths are generally revised upward by the time the next weekly report is released.

In their report, the modelling group found that weekly hospital admissions were being under-reported by an average of 25 per cent.

"This is like comparing apples to oranges,'" Otto said. "You can't compare a partial number this week to a more complete number from the week before."

When asked why numbers are always revised upwards in weekly reports, a spokesperson for the Health Ministry said that "retroactive refreshes of the data are a normal part of public health surveillance systems."

"It is expected that the number of hospital admissions, critical care admissions and deaths reported will increase over time as data feeds to BCCDC are updated," the spokesperson said in a statement.

Otto said there should be stronger public health messaging about the importance of masks, specifically, and the report noted that getting boosted can reduce the impact of the fall wave of COVID.

"We have not seen the BA.5 wave really come down and we know that people's immunity is waning from … vaccinations early in the year," Otto said.

"We're also not seeing a major uptake of the [booster] vaccines."