Thread by @TRyanGregory

For anyone still clinging to the "Omicron is mild" myth, let me remind you what has happened here in Canada (which had one of the least awful overall outcomes in Europe and the Americas, and with similar or worse patterns occurring in many other places). 🧵

In my view, the "subvariants" of "Omicron" are divergent enough to warrant their own designations with Greek letters, but the WHO has opted to call everything "Omicron". One can't have it both ways, so that means the waves caused by BA.1, BA.2, and BA.5 all count as "Omicron".

In Canada, the first Omicron wave (BA.1) reached the highest peak in hospitalizations and the second highest peak in daily deaths -- behind only the second wild type wave in 2020. Those initial waves occurred before vaccines or any "hybrid immunity" had built up.

From the start of the pandemic to the start of the first Omicron wave (Mar. 9, 2020 to Dec. 31, 2021; 662 days) there were 30,320 COVID deaths in Canada. From Jan. 1, 2022 to the time of this writing (data for Aug. 26, 2022; 237 days), there were 13,729 deaths.

That works out to an average of 46 deaths per day before Omicron and 58 deaths per day since Omicron. As a reminder, that first number includes the initial waves and the period before vaccines were available. when the impacts were especially severe for the most vulnerable.

It may be that the risk of severe illness or death is lower on a *per infection* basis with Omicron thanks to vaccines and/or immunity due to prior infection, but *overall* Omicron has not been milder.

This is because severity per infection represents only one half of the equation. The other major factor is the number of infections. Omicron variants can escape immunity, prior immunity is waning, and reinfections are becoming more common.

And all of this deals only with the impacts of acute infection. Long COVID remains a major risk, even with mild initial infection. Each reinfection adds to the total risk (even if the relative risk is lower for each re-infection, the total risk is higher with more infections).

It is also worth noting that all of this is the result of variants within a single "Omicron" clade. Omicron was not derived from Delta, and Delta was not derived from Alpha. The even bigger concern is something quite new evolving. The more transmission, the more new variants.

*first wild type wave