Multifaceted strategies for the control of COVID-19 outbreaks in long-term care facilities in Ontario, Canada (preprint)

ABSTRACT

BackgroundCOVID-19 has caused severe outbreaks in Canadian long-term care facilities (LTCFs). ObjectiveTo evaluate the effect of mitigation measures in LTCFs including routine testing of staff and vaccination of staff and residents. DesignAgent-based transmission model parameterized with disease-specific estimates, temporal sensitivity of nasopharyngeal (NP) and saliva testing, preliminary results of vaccine efficacy trials, and data from initial COVID-19 outbreaks in LTCFs in Ontario, Canada. SettingCharacteristics of staff and residents were included in the model with age-dependent risk of hospitalization and deaths, calibrated to the cumulative incidence of COVID-19 reported in these settings. ParticipantsSynthetic staff and resident populations. InterventionsRoutine NP and saliva testing of staff; vaccination of residents and staff. MeasurementsDaily incidence and attack rates in the LTCF using large-scale model simulations; estimates of hospitalizations and deaths and their 95% credible intervals. ResultsWeekly routine testing of staff with 2-day turnaround time reduced infections among residents by at least 20.3% (95% CrI 18.7-21.8%), compared to baseline measures of mask-wearing, symptom screening, and staff cohorting alone. A similar reduction of hospitalizations and deaths was achieved in residents. Vaccination averted 2-4 times more infections in both staff and residents as compared to routine testing, and markedly reduced hospitalizations and deaths among residents by 81.4% (95% CrI 80.6-82.2%), and 82.1% (95% CrI 81.5-82.7%), respectively. LimitationsTimelines of vaccine distribution and compliance rates with routine testing are key parameters affecting strategy outcomes. ConclusionRoutine testing of staff reduces silent transmission in LTCFs. Vaccination could have a substantial impact on mitigating disease burden among residents, but may not eliminate the need for other measures before population-level control of COVID-19 is achieved.