The Delta variant has become a game-changer in Ontario’s ability to achieve herd immunity against COVID-19.
A new report by Public Health Ontario (PHO) about what the pandemic will look like this fall and winter says achieving herd immunity won’t happen without an approved vaccine for children under 12.
The report points the finger at the Delta Variant, now the dominant variant in Ontario and much of the world. Due to Delta’s increased transmissibility and potential for breakthrough infections among those who are vaccinated, the report says the percentage of the population requiring vaccination to hit a point where virus transmission enters long-term decline now exceeds the number of people actually medically eligible for vaccination at this time.
“The critical threshold for vaccination is now estimated to be at least 90 per cent of the Ontario population, and over 100 per cent of the vaccine-eligible population,” Public Health Ontario says.
To fully exit Ontario’s reopening plan, the original target vaccination rate was 75 per cent of people over 12 fully vaccinated, 80 per cent with at least one dose and no region with less than 70 per cent fully vaccinated.
PHO says the target was developed with the Alpha variant in mind, which according to provincial research was far less deadly than Delta.
Until the 90 per cent vaccination target is achieved, Ontario Chief Medical Officer of Health Dr. Kieran Moore expects waves of COVID-19 for the next six to eight months.
An approved vaccine for children under the age of 12 is still at least months away.
“Individuals under 12 years of age will not be vaccinated when they are expected to return to in-person learning in September, and are therefore a population where Delta will circulate as more community-level public health measures are lifted,” according to the PHO report.
Herd immunity is broadly defined as the point at which enough members of the population have resistance to infection by a pathogen either by antibodies generated through prior infection or vaccination.
Public Health Ontario suggests developing different thresholds for COVID-19 cases warranting further action in daycares and elementary schools, where children will be unvaccinated, versus secondary schools where children are eligible for vaccination.
They also suggest encouraging parents of elementary and daycare-age kids to get vaccinated.
“It may be useful to survey the vaccination status of eligible household members living with the children attending childcare and elementary schools to identify opportunities to support vaccine confidence and uptake and thereby reduce the risk of chains of transmission extending to households or childcare/school settings.”