BC COVID situation ‘good and improving’, but B.A.2 poses modest threat: modelling group

The risks from an increase in B.A.2 COVID cases are modest over the next few months in BC even with the lifting of many public health measures, according to a new report from the independent BC COVID-19 Modelling Group.

The report says that BC’s COVID situation is “good and improving” at the moment.

However, while cases, hospitalizations, and ICU admissions in the province have dramatically reduced—around threefold from the height of the Omicron wave—the spread of B.A.2, a sublineage of the Omicron variant that’s growing in prevalence, represents a risk in BC’s near future.

B.A.2 is already presumed to comprise more than half of new COVID cases in the province, and the report says the steep drop in cases is mostly due to a decline of B.A.1 (what we know as Omicron). While the absolute number of cases is reducing, the report says frequency of B.A.2 is slowly growing.

While the rate of B.A.2 cases is still fairly low both here and in Ontario, the report’s authors say that waning immunity to COVID, along with the relaxation of many public health measures, poses the threat of another Omicron wave.

But with high levels of immunity in the general public in BC at the moment, it’s possible that another Omicron wave would be much less severe than the last one that began in December and peaked in January.

“Rises in cases should be moderate over the short term, especially if we continue to practice protective health measures (masking, improving ventilation, and seeking spaces with sufficient levels of ventilation when gathering),” the report says.

The BC government has justified the removal of many public health measures, including masking, by pointing to data that shows British Columbians have a high level of immunity against COVID. More than 90% of people in the province are double-vaccinated or have immunity from a recent infection.

However, the report points to data from the UK that shows that the effectiveness of a booster vaccine in preventing symptomatic infection wanes from 70% to about 40% after 15 weeks.

“These studies find that boosters provide ~10-fold protection against hospitalization, compared to unvaccinated individuals, but this drops to four- to five-fold after three to four months since boosting,” the report says.

“As a consequence of this waning, the risk of hospitalization for a boosted individual rises by about twofold over the course of three to four months.”

The authors say a fourth vaccine dose, administered three to four months after a third dose, would reduce the risk of hospitalization in those most susceptible to severe illness. They do note that boosters have been effective in fighting off Omicron, in spite of several genetic changes in the variant compared to previous ones like Delta.

The authors say it’s tough to accurately measure the effects of public health orders like mandatory masking being lifted, because it largely depends on the individual behaviours of those who continue to practice them.

The evidence, however, points to well-fitting and high-quality masks as a tool that substantially reduces the risk of COVID transmission.

And with many regions in Canada moving away from requiring masks, the report says there should now be an emphasis on creating safer indoor spaces with improved ventilation and carbon dioxide monitoring systems.

“Everybody in BC should continue to have safe access to essential services, such as transportation and groceries, especially while Omicron remains prevalent,” the report reads.