The number of people sick with COVID-19 in British Columbia is probably 100 times higher than what is actually being reported, according to new independent modelling.
The Wednesday report from the BC COVID-19 Modelling Group also concludes that the BA.5-driven Omicron wave has peaked in the province and across much of Canada, owing to increased population-level immunity.
Still, the prevalence of the virus means people should consider whether they should be taking better precautions to protect themselves, including wearing a mask and ensuring their vaccinations are up to date, Dr. Sally Otto, a UBC researcher and a member of the modelling group, said in an interview.
The group uses data from the COVID-19 Immunity Task Force and Canada Blood Services survey on antibodies to SARS-CoV-2, which say the vast majority of British Columbians have antibodies to the virus, either through vaccination, previous illness or both.
The data also suggest that more than 50 per cent of British Columbians had been infected with the virus by the end of June. That means over 2.5 million people in the province have been infected at this point, Dr. Otto said. But there have only been about 120,000 cases reported for 2022, she added.
“That shows you this big discrepancy,” Dr. Otto said. She said the public should be given the information they need to make decisions about the risks that they’re willing to take.
“I think if more people knew how prevalent the virus was at the moment, they’d just be more careful to wear masks, they might be more likely to get boosted and they would be more likely to protect those around them by avoiding crowded indoor situations.”
Late last year, B.C. joined other provinces by limiting access to the gold-standard polymerase chain reaction, or PCR, lab test. Cases recorded by BC Centre for Disease Control (BCCDC) are based solely on positive PCR tests, but there are very few of them done.
New numbers released Thursday by the BCCDC showed that 877 cases were recorded between Aug. 7 and 13. There were 181 hospital admissions in that period and 24 deaths.
The modelling group’s report suggests deaths as a result of COVID-19 may be under-reported by a factor of two based on excess mortality – the number of deaths beyond what is expected in a specific period.
B.C.’s Provincial Health Officer Bonnie Henry said in a statement that public health uses a variety of indicators, such as waste water testing, to understand COVID-19 transmission rates in addition to PCR testing.
She also pointed to the example of repeated serosurveys over the course of the pandemic. She said they have provided a good sense of infection rates which, depending upon age group and stage of the pandemic, suggest there may be up to 10 times more cases than PCR-confirmed reports.
Dr. Henry said models are a tool and provide a sense of what could occur, but that pandemics are dynamic and many factors should be considered before drawing conclusions from modelling exercises.
“As we move into the respiratory illness season, everyone should remember COVID-19 continues to circulate throughout the community. People should stay vigilant, practise COVID-19 safety precautions as needed, and keep their vaccines up-to-date,” her statement reads.
The modelling group’s report says the spread of COVID-19 in 2022 is greatly influenced by population-level immunity. The turnaround in the growth of BA.2 infections happened because of the increasing immunity, primarily from new cases of the variant and not because of changes to public-health measures or personal behaviour, according to the report.
“Good news is the high level of immunity that we have in the population due to vaccines, previous infections, or both, has turned around the BA.5 wave sooner than it could’ve,” Dr. Otto said.
However, she said the high level of immunity doesn’t mean people have enough of antibodies to ward off a virus infection: “That’s the waning that we’re seeing in people. Antibody levels decline, and (people) get more susceptible to getting infected.”
The modelling group projects that infection risks remain high in B.C. but are likely to decline through August.
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