Table 6.
Evolution of WWS relation to clinical epidemiological metrics throughout the studied period of the COVID-19 pandemic.
| Surge | Vaccination immunity | Natural immunity | WWS relation to clinical metrics | HW ratio |
|---|---|---|---|---|
| Alpha (Apr. 8th, 2020, to Jul. 31st, 2021) | <70 % of total population fully vaccinated (two doses of approved vaccine) | Limited natural immunity as this surge is the first exposure to the COVID-19 disease for the majority of the infections | WWS strong and moderate correlations to both incidence (ρ = 0.821 at △t = 5d in Ottawa and ρ = 0.655 at △t = 10d in Hamilton) and hospitalizations (ρ = 0.808 at △t = 10d in Ottawa and ρ = 0.682 △t = 14d in Hamilton) | Elevated ratio, indicative of virulent dominant VOC |
| Delta (Jul. 31st, 2021–Dec. 12th, 2021) | Significant vaccination immunity with ≥70 % of total population fully vaccinated against COVID-19 (two doses of approved vaccine) with limited waned immunity with vaccine efficacy against the Delta VOC being 75 % at 17 weeks since reception of a second COVID-19 mRNA vaccine dose | Higher natural immunity, and limited vaccine immune escape (indication of re-infection from Alpha VOC) | WWS very weak correlation to incidence (ρ = 0.189 at △t = 0d in Ottawa and ρ = −0.029 at △t = 0d in Hamilton) (this shown to decrease) and weak correlation to hospitalizations (ρ = 0.364 at △t = 11d in Ottawa and ρ = 0.312 at △t = 5d in Hamilton) | Elevated ratio, indicative of virulent dominant VOC |
| Omicron (BA.1) (Dec. 12th, 2021–Mar 27th, 2022) | Waned vaccination immunity for individuals receiving two doses of vaccine 5 months from the onset of the Omicron (BA.1) VOC | Limited natural immunity, and significant immune escape via VOC | WWS strong correlation to incidence again (ρ = 0.861 at △t = 0d in Ottawa and ρ = 0.727 at △t = 0d in Hamilton) and a strong correlation to hospitalizations (ρ = 0.947 at △t = 4d in Ottawa and ρ = 837 at △t = 3d in Hamilton) | Elevated ratio indicative of virulent dominant VOC |
| Omicron (BA.2) (Mar. 27th, 2022–May 26th, 2022) | Significant vaccination immunity (due to rollout timing of booster vaccine dose) | Higher natural immunity (indication of re-infection from Omicron BA.1 VOC) | WWS moderate and strong correlation to incidence again (ρ = 0.579 at △t = 0d in Ottawa and ρ = 0.847 at △t = 0d in Hamilton) and strong correlations to hospitalizations (ρ = 0.784 at △t = 5d in Ottawa and ρ = 0.612 at △t = 3d in Hamilton) (weaker compared to preceding the Omicron BA.1 surge due to lower morbidity) | Low ratio, indicative of less virulent dominant VOC |