This chart compares Canada’s pandemic journey over the past three months with those of other nations with comparable vaccination levels.  As shown in the chart, BA.5 hit Portugal a month earlier than the rest of this set of countries. While Portugal’s infections soared through most of June, new cases continued to decline as the BA.2 wave ebbed. As death rates tend to lag new cases by nearly a month, new Canadian deaths from BA.5 infections have only recently resumed their rise. 

The graph lines demonstrate the degree to which every country’s pandemic journey differs depending on both recent and past policy and individual choices. Rates of new infections rise with each successive arrival of a more infectious variant and decline when that variant starts running out of new victims. Who gets victimized is a combination of opportunity (usually close indoor contact with no or insufficient masking) and potential victim’s level of immunity (whether from previous infection, vaccination or both).  Boosters are important because immunity wanes with every passing month. BA.5 is especially adept at evading immunity.

Note that death rates inevitably rise and fall several weeks after corresponding trends in new infections, but nowhere near as steeply. That’s because our bodies generate two different kinds of immunity in response to new pathogens. Humoral immunity, involving the antibodies which prevent infection, wanes fairly quickly. By contrast, cellular immunity (based on the propogation of suitably-primed B- and T-cells) determines how quickly and successfully we can defeat an established infection and therefore how well we can recover. Since cellular immunity is far more durable, those who are vaccinated or had a previous COVID infection remain vulnerable to new BA.5 infections but are less likely to be hospitalized or to die. 

Second and more important, these and other nations’ experiences show that Delta can be stopped, but its much-increased transmissibility and partial vaccine resistance render that much harder to accomplish than for previous waves. The common thread which differentiates those which have succeeded has been retaining or re-imposing locally-appropriate elements of the broad suite of proven public health interventions, the simplest of which is mandatory masking for indoor public spaces. Because pandemic control gets exponentially harder the higher the rate of new cases, successful pandemic management requires decisive action (for example, the Netherlands’ re-imposition of restrictions within a few days of the Delta wave manifesting), not the chronic foot-dragging exhibited by so many Canadian leaders throughout this pandemic, which has only served to multiply the death toll.

Following the pattern of the other nations whose recent pandemic experiences to date are illustrated in this path, Canada’s seventh wave is likely to be a severe one. By September, we will have lost the seasonal advantage of spending much more of our time outdoors. Our average humoral immunity continues to decline due to more of us echewing booster shots. And, relatively few of us continue simple precautions like mask wearing and modest social distancing. In combination, we’re essentially asking to be infected and BA.5 is well positioned to leverage those opportunities.