In a large province-wide health region with free universal access to SARS-CoV-2 vaccines, our population-based study reinforces how an unvaccinated population has a far greater likelihood of ICU admission and excess health resource use due to COVID-19 infection than a population vaccinated against COVID-19 with breakthrough infection.15 We found that unvaccinated persons, particularly within the age strata of 50–79 yr, accounted for more than 1,000 potentially avoidable ICU admissions, 13,000 potentially avoidable ICU bed-days, and CAD 61 million in excess healthcare costs during only the four-month COVID-19 wave dominated by the delta variant-of-concern. Had this unvaccinated population been fully vaccinated, substantial excess health resource use and costs could have been avoided, and strain across the health system could have been mitigated. Strain on the ICU and hospital capacity has been strongly associated with incremental and excess attributable mortality during the COVID-19 pandemic.16,17 This has necessitated considerable reorganization of health services and reallocation of health resources during the delta variant-of-concern wave, such as redeployment of healthcare professionals, deferral of routine health services, and postponement of scheduled procedures and surgeries.

Vaccines are highly cost-effective population health interventions because of their proven capacity to reduce avoidable deaths, defer healthcare costs, and prevent long-term disability attributable to communicable diseases.18,19 Similar data on the broad patient, health system, and society benefits of vaccination against SARS-CoV-2 from varying jurisdictions have now been shown.18,20,21 In a modelling study of the Italian population, widespread vaccination was predicted to effectively reduce hospitalizations by 74.9% (2,379,144 hospitalizations avoided) and ICU admissions by 71.3% (259,224 ICU admissions avoided), and over EUR 2.9 billion (CAD 3.95 billion) in avoided healthcare costs in 2021.21 In an economic modelling study in the USA, widespread SARS-CoV-2 vaccination was estimated to generate USD 5 trillion (CAD 6.1 trillion) in societal economic benefits. These benefits were attributed largely to avoided SARS-CoV-2 infections (with reduced hospitalizations and rehospitalizations), reduced medical conditions exacerbated by the pandemic (e.g., mental health impairment and depression), more lives saved from fewer COVID-19 infections, and the earlier lifting of public health restrictions with more rapid resumption of normal economic activity and gains to the USA’s gross domestic product.18 The societal benefits extend well beyond COVID-19-specific infections and attributable deaths. A substantial increase in excess deaths was observed in the USA during the early phases of the pandemic when vaccines were not available, with a large proportion attributed to causes other than COVID-19, such as heart disease, diabetes, and nonrespiratory related disease.5,6,22 This excess mortality may be related to delayed or impeded access to acute care and strained health systems.17

This study has limitations. First, we used aggregate data on vaccination status and lengths of stay that were age adjusted only and do not account for comorbidity and acuity. Second, estimated bed-days and costs per ICU bed-day were aggregated for the total and age-stratified patients with COVID-19 and were not specifically stratified by vaccination status. Further, these estimates represent the ICU only and do not capture total hospitalization. Nevertheless, the data used to derive estimates were real-world, population level and included vaccination status and health services use. Lastly, these data were derived in Alberta and may have limited generalizability to other health jurisdictions. Nevertheless, similar resource and cost avoidance would be likely under comparable conditions.

In conclusion, our findings have important implications for discourse on the relative balance of increasingly stringent public health protection (restrictions), including mandatory vaccination policies, and the sustainability and function of health system infrastructure and capacity during the ongoing COVID-19 pandemic.23