Modelling the impact of age-stratified public health measures on SARS-CoV-2 transmission in Canada.

Vanessa Gabriele-Rivet,Lisa A Waddell,Patricia Turgeon,Kelsey L Spence,Nicholas H Ogden,Ainsley Otten,Aamir Fazil,Victoria Ng

doi:10.1098/rsos.210834

Vanessa Gabriele-Rivet, Lisa A Waddell + Show 6 more

Open Access

https://doi.org/10.1098/rsos.210834

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Abstract

Public health measures applied exclusively within vulnerable populations have been suggested as an alternative to community-wide interventions to mitigate SARS-CoV-2 transmission. With the population demography and healthcare capacity of Canada as an example, a stochastic age-stratified agent-based model was used to explore the progression of the COVID-19 epidemic under three intervention scenarios (infection-preventing vaccination, illness-preventing vaccination and shielding) in individuals above three age thresholds (greater than or equal to 45, 55 and 65 years) while lifting shutdowns and physical distancing in the community. Compared with a scenario with sustained community-wide measures, all age-stratified intervention scenarios resulted in a substantial epidemic resurgence, with hospital and ICU bed usage exceeding healthcare capacities even at the lowest age threshold. Individuals under the age threshold were severely impacted by the implementation of all age-stratified interventions, with large numbers of avoidable deaths. Among all explored scenarios, shielding older individuals led to the most detrimental outcomes (hospitalizations, ICU admissions and mortality) for all ages, including the targeted population. This study suggests that, in the absence of community-wide measures, implementing interventions exclusively within vulnerable age groups could result in unmanageable levels of infections, with serious outcomes within the population. Caution is therefore warranted regarding early relaxation of community-wide restrictions.

Highlights

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pathogen responsible for coronavirus disease (COVID-19), was detected in Wuhan, China in late 2019 [1]
Compared with the benchmark scenario, which generated steady epidemic curves across time with a median fluctuating around 10 cases per 100 000 people, all age-stratified intervention scenarios, with removal of public health measures (PHMs), led to a substantial increase in the median attack rate and an exponential growth in the daily incidence curves
Across all age-stratified interventions explored in the present analyses, the younger population experienced considerably worse outcomes compared with the benchmark scenario with sustained community-wide measures, suggesting that this approach would lead to levels of infections among this age group that result in a large number of avoidable deaths

Summary

Introduction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pathogen responsible for coronavirus disease (COVID-19), was detected in Wuhan, China in late 2019 [1]. Proponents for the age-stratified implementation of PHMs hypothesize that by focusing on protecting only vulnerable populations, while others resume life as normal without any restrictions as a means of gradually achieving herd immunity, the occurrence of severe health outcomes and societal and economic disruption could be minimized [9]. The principles of this declaration have been used to oppose restrictive PHMs and have been considered in policy decisions [13,14]

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