Emerging Omicron subvariants have potential to lead to a spike in COVID-19 cases

Recent news reports have highlighted the concerns of Canadian infectious diseases experts regarding the emergence of two new subvariants of the Omicron strain of COVID-19—which could stimulate an increase in the number of COVID-19 cases and hospitalizations in Canada this fall and winter.1-3 The two new variants—BQ.1.1 and BA.2.75— have been reported in multiple countries. However, it is too early to determine whether either of these new subvariants could become a dominant COVID-19 strain globally.1 BQ.1.1 has been reported in Nigeria, United Kingdom, Japan, United States, France, Belgium, Denmark and Italy.4 As of October 3, 2022, 12 cases of BQ.1.1 had been documented in Canada.4 Although BQ.1.1 currently comprises only a small proportion of all COVID-19 cases globally, in some settings the proportion of cases is increasing at a rate that suggests increased transmissibility relative to other circulating variants.4 The spike protein mutations found in BQ.1.1 are also concerning due to their potential to cause significant immune escape. However, little evidence exists on BQ.1.1 transmissibility, immune evasion ability and disease severity, so the risk to Canadians is still uncertain.4 As of September 19, 2022, global prevalence of BA.2.75 and its sublineages was less than 0.5%. However, BA.2.75 and its sublineages are dominant in India (83% of all analyzed sequences from August 16–29, 2022). In Canada, BA.2.75 and its sublineages accounted for 0.85% of all sequences analyzed between August 30–September 12, 2022.5 Current evidence suggests that BA.2.75 and its 21 sublineages may have higher transmissibility and infectivity than BA.5 and BA.2, higher potential than BA.2 (but not BA.4 or BA.5) for causing severe disease and evading immunity from vaccination and prior infection.5 READ: Health officials hope newly approved BA.4, BA.5 Omicron-targeted vaccine will improve booster uptake For the week ending September 18, 2022, the Omicron BA.5 subvariant continued to predominate, accounting for 91% of all COVID-19 cases in Canada, followed by BA.4 (7.3%) and BA.2 (1.6%).6 While it is unclear what level of protection vaccines may provide against BQ.1.1. or BA.2.75, infectious disease experts have stated that there is no reason to believe that either subvariant is sufficiently different enough to completely diminish the protective benefits of vaccination. To date, with every variant seen so far (Alpha, Delta, Omicron BA.1, Omicron BA.2, Omicron BA.5), vaccines have been very effective in providing protection against severe infection, such as hospitalization and death.2 While new variants are expected to emerge from time to time, it is hoped that these waves will have less and less of an impact on Canadian society as we increase our level of immunity, through vaccination and antibodies stimulated by COVID-19 infection.2 Experts will continue to monitor for the spread of these and other subvariants that could end up factoring into future waves of the pandemic. In the meantime, the public should be encouraged to stay home when sick or when they have symptoms of illness, wash hands frequently and wear a mask especially when indoors in areas with lots of people.2 A fall COVID-19 vaccine booster dose is also recommended, preferably with a bivalent Omicron-containing mRNA COVID-19 vaccine (for authorized age groups), regardless of the number of booster doses previously received.7 READ: POLL: How much demand do you anticipate for the new bivalent COVID-19 vaccine? References 1. Bowden O. What are BA.2.75 and BQ 1.1? The two emerging COVID-19 subvariants raising concern among infectious disease experts. CTV News October 7, 2022. https://www.ctvnews.ca/health/coronavirus/what-are-ba-2-75-and-bq-1-1-the-two-emerging-covid-19-subvariants-raising-concern-among-infectious-disease-experts-1.6100637 (accessed October 12, 2022). 2. Fox C. Experts keeping close eye on new COVID subvariants in Ontario ahead of winter. CTV News October 5, 2022. https://toronto.ctvnews.ca/experts-keeping-close-eye-on-new-covid-subvariants-in-ontario-ahead-of-winter-1.6097587 (accessed October 13, 2022). 3. Miller A. New Omicron strains on the horizon could drive future COVID waves. CBC News October 1, 2022. https://www.cbc.ca/news/health/omicron-subvariants-immune-escape-bivalent-vaccines-1.6601218 (accessed October 13, 2022). 4. Public Health Ontario. Evidence brief. Risk assessment for Omicron sublineages BQ.1 and BQ.1.1 (as of Oct 5, 2022). https://www.publichealthontario.ca/-/media/Documents/nCoV/voc/2022/10/omicron-bq1-bq11-oct-5.pdf?sc_lang=en (accessed October 13, 2022). 5. Public Health Ontario. Evidence brief. Risk assessment for Omicron sub-lineage BA.2.75 (as of September 23, 2022). https://www.publichealthontario.ca/-/media/Documents/nCoV/voc/2022/06/eb-omicron-variant-sub-lineage-BA-275.pdf?sc_lang=en (accessed October 13, 2022). 6. Government of Canada. COVID-19 epidemiology update. Figure 2. Weekly variant breakdown Updated: October 7, 2022. https://health-infobase.canada.ca/covid-19/ (accessed October 13, 2022). 7. National Advisory Committee on Immunization (NACI). An Advisory Committee Statement (ACS). Updated guidance on COVID-19 vaccine booster doses in Canada. October 7, 2022. https://www.canada.ca/content/dam/phac-aspc/documents/services/immunization/national-advisory-committee-on-immunization-naci/guidance-covid-19-vaccine-booster-doses.pdf (accessed October 13, 2022).

Emerging Omicron subvariants have potential to lead to a spike in COVID-19 cases

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