Brooks Fallis is a critical care physician and the former medical director and division head of critical care at the William Osler Health System.

The rapid development and subsequent Canada-wide roll out of vaccines has been remarkable. Unfortunately, global experience coupled with epidemiological calculations tell us that vaccines alone are not enough to stop the spread of the super-transmissible and more deadly Delta variant. Yet provinces from British Columbia to Quebec are reopening using vaccine thresholds that are too low to achieve herd immunity, which in Delta’s case would likely require immunity through vaccination or infection of greater than 90 per cent of the entire population. Fully reopening with a vaccine-only strategy will backfire and lead to a fourth wave of the virus.

Provinces that wait too long to intervene will find themselves stuck with two unpalatable options: resume heavy restrictions to regain control, or let COVID-19 spread. While politically unappealing, we need to refocus on transmission reduction.

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Hospitalizations and deaths per case will be lower than previous waves thanks to vaccines. But milder symptomatic infection is happening among the vaccinated, and there is evidence that vaccinated people can still transmit the virus to others. That means COVID-19 will continue to circulate and find the unvaccinated and most vulnerable. There are also concerns about waning immunity months after vaccination, the effects of long-COVID and the potential emergence of new variants that could be resistant to our current cohort of vaccines.

Shots are not yet approved in children under 12, and in just a few weeks millions of them will enter indoor environments, many of which are crowded and poorly ventilated. Hospitalization and death are much less common in children than in adults, however, if large numbers become infected, children’s hospitalizations will be significant, as is currently occurring in parts of the United States. But hospitalization and death are not the only bad outcomes: What is called “long COVID” can be debilitating, and the virus’s impact on the developing brain is not well understood.

Simply put: A vaccine-only strategy is short-sighted and reckless.

Canada needs a comprehensive solution that incorporates population immunity and transmission reduction, coupled with continued cluster control through test-trace-isolate-support systems (including a strong paid sick-leave program), border control and surveillance.

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To date we have relied on crude and underdeveloped transmission-reduction strategies: limiting indoor gatherings, low-quality masks and lockdowns. Overwhelming evidence now demonstrates that the dominant mode of transmission of SARS-CoV2 is airborne, yet mitigation strategies have not evolved with this knowledge.

Indoor environments where people are in close contact present the highest risk for transmission. Work-from-home should continue as much as possible, as it is premature to return to the office unless absolutely necessary. When indoor close contact is occurring, cloth or medical masks should be replaced with respirator masks, which provide superior protection through a combination of exhalation source control and inhalational filtration.

Broad improvements in ventilation and filtration offer the greatest untapped opportunity to tackle airborne spread. Improving air quality in schools and other indoor settings can reduce total infections, limit superspreader events, and likely decrease transmission of other respiratory viruses including influenza. Furthermore, studies have shown that investments in school ventilation may actually improve performance in kids. Partnerships with engineers and aerosol scientists are long overdue, as these interventions are outside the expertise of public health and medical doctors. If SARS-CoV-2 evolves and vaccine efficacy weakens, this is the greatest investment we could make in preparation.

Vaccines still remain the best way to safely maximize population immunity, which is why continuing efforts to reach everyone and promote equity of access through family doctors and trusted community organizations is essential. As well, we need some sort of passport system: Mandatory vaccination should be implemented and enforced in high-risk settings where indoor engagement is unavoidable, such as in schools, hospitals and long-term care homes. Private enterprises, particularly high-risk environments such as gyms, warehouses, factories, restaurants and meat-packing plants, should also invoke mandatory vaccination to protect their employees and their businesses.

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Canadian policy-makers (outside of the Atlantic provinces and the territories) have underestimated COVID-19 with each reopening effort, and this time will not be different. Vaccines are an incredible asset, but a vaccine-only solution is inadequate against Delta – and new variants of concern may appear, particularly as the global picture worsens.

Nobody knows with certainty what will happen next with COVID-19. But despite our pandemic exhaustion, SARS-CoV2 continues to evolve, and so too must our infection mitigation strategies.

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