The good and bad news on Omicron subvariant BA.2 as it continues to spread in Ontario

What the presence of the more contagious ‘stealth Omicron’ means for the province as it prepares to lift public health restrictions.

thestar.com
May Warren and Kenyon Wallace
Feb. 24, 2022

While the heightened infectiousness of BA.2 means it could be on its way to overtaking BA.1 as the most dominant form of Omicron in Ontario, early evidence suggesting it causes no more serious outcomes than the original version has experts expressing cautious optimism.

But they warn that with the lifting of COVID-19 public health restrictions next week, there are many unknowns about what is in store for Ontario in the coming months.

“Currently everything looks great. Cases are dropping, hospitalizations are dropping, ICUs are being decompressed, deaths are going down, and by and large in most provinces the wastewater signals are in decline,” said Dr. Isaac Bogoch, an infectious diseases specialist at University Health Network. “On the other hand, it’s still winter. There are still a lot of people congregating in indoor settings where there will be opportunities for the virus to transmit. Plus, we’ve got the lifting of many public health measures. Plus, we’ve got BA.2.”

He added that these factors could mean a slowing in the decline of cases, a plateau or even a bump in numbers.

“I think we should just acknowledge there is uncertainty in the road that lies ahead.”

Omicron is still by far the dominant variant in the province, but the proportion of COVID-19 cases in Ontario that are the BA.2 subvariant increased from two per cent in the Jan. 16-22 period to 4.4 per cent between Jan. 23-29, according to Public Health Ontario’s most recent epidemiological summary.

Early evidence suggests that BA.2 is inherently more transmissible than BA.1, but the latter remains the most common version of Omicron reported worldwide, according to the World Health Organization. In a statement Tuesday, the WHO noted that, globally, the proportion of BA.2 sequences has been increasing compared to BA.1 in recent weeks, although the circulation of all variants is declining.

Countries should continue to be “vigilant” and keep up monitoring of this subvariant, the WHO added.

The two pieces of good news reported by the global health agency: early clinical data from several countries showed no difference in severity between BA.1 and BA.2; and those infected with BA.1 have strong protection against reinfection with BA.2.

“We can expect that our wall of immunity that we built up through three-dose rollout and infection will hold,” said Dr. Peter Jüni, scientific director of Ontario’s COVID-19 Science Advisory Table. “We also see preliminary data that suggests that it’s not the case that BA.2 results in higher risk of serious outcomes such as hospitalization, ICU admission or death than BA.1. We don’t have evidence to suggest that. All of that taken together is actually quite good news. We can be carefully optimistic.”

In Ontario, as of mid-February, 20 per cent of eligible COVID positive polymerase chain reaction (PCR) tests are now sent for whole genome sequencing necessary to determine if they are the BA.2 subvariant, sometimes called “stealth Omicron” because it’s harder to detect. That’s up from only five per cent last month.

That means the province’s current testing regime, which is also limited to only high-risk people and settings, is missing many cases.

Catalina Lopez-Correa, the chief scientific officer for Genome Canada, a non-profit funded by the federal government, which invests in genomic science and technology, said the magic question is always how much testing is enough.

But the surveillance capacity has increased in Canada since the beginning of the pandemic, she said, as has data-sharing between provinces and at the international level.

“Even though we’re all concerned about this Omicron subvariant, I think there are reasons to be optimistic,” she said, noting that while everyone is tired of COVID, “the pandemic is not finished.”

As provinces drop health restrictions it now falls more on individuals to protect themselves through measures like vaccination, she said.

Omar Khan, a professor of Biomedical Engineering and Immunology at the University of Toronto, agrees that there is a lot of uncertainty ahead, particularly around reinfection risk.

Omicron vaccines, which Pfizer and Moderna are both trying to develop, would help, said Khan, who is also a Canada Research Chair in Nucleic Acid Therapeutics.

Making sure that everyone has access to vaccines, regardless of where they live, he said, is key to preventing more potential variants and subvariants.

When the virus runs wild in a community “it can find the holes, and find the niche where it can breed and develop,” Khan added.

“We can’t have stability locally until we see it globally.”

BA.2 has been spreading quickly in a handful of countries, including Denmark and India.

A recent pre-print study out of Denmark looked at 47 people who became infected with BA.2 shortly after infection with BA.1. It found that reinfection, while possible, was rare. The majority of the patients were unvaccinated, under 20 years of age, and none were hospitalized or died.

The study is not yet published in a peer-reviewed journal, considered the gold standard in scientific research.

Jüni anticipates further waves of infection globally, which means COVID is not yet endemic.

“The problem is, if these waves are too high in Canada, our health-care systems might start to be challenged again,” he said, adding we should be ready to bring back some lighter public health measures, such as updated vaccines, vaccine certificates and masks, as well as improved ventilation, that will not severely impact our society and economy.

“This is not going back to the lockdown blues of 2020. Not at all if we’re a bit smart.”