Exit plans modelled by Imperial’s MRC Centre for Global Infectious Disease Analysis highlight the risks of easing restrictions too quickly.
The report, which, along with work from the University of Warwick, is informing England’s ‘roadmap’ out of lockdown, modelled multiple scenarios for lifting non-pharmaceutical interventions (NPIs) under different vaccine rollout speeds.
The current numbers of COVID-19 cases are higher than seen last summer when England came out of its first lockdown. Under all scenarios considered, the modelling projects there will be an increase in the level of infections as controls are relaxed. Even with vaccines and NPIs in place, the estimates suggest there is a risk of tens of thousands additional COVID-19 related deaths by Summer 2022 in England.
Proceeding with caution
The report, which was reviewed by SPI-M and SAGE but not yet by a peer-reviewed journal, finds that NPIs must be lifted slowly and cautiously to minimise the number of deaths, and prevent hospitals becoming overwhelmed. The analysis shows that baseline NPIs (such as handwashing, mask wearing in crowded places, and compliance to contact tracing and self-isolation of cases) must remain in place and adhered to, throughout 2021 and beyond. Due to the considerable uncertainty around the impacts of each stage of relaxation, the researchers argue it is critical to assess the impact of each relaxation and the vaccination programme before committing to the next phase.
The researchers explain that despite the encouraging success of the vaccination programme, vaccines alone will not be sufficient to keep the epidemic under control unless a high proportion of the population are vaccinated (likely including children). This is because not everyone will be eligible for vaccination (such as people who are under 18 and those allergic to components of the vaccine), and some may refuse the vaccine. However, if the effectiveness of vaccines and uptake (especially amongst the younger age groups) is higher than assumed in this analysis, the number of hospitalisations and deaths might be lower than projected.
The team explains that it is not possible to predict exactly how the individual policies will affect the epidemic, and the impact of waning immunity and other emerging variants is particularly difficult to assess at present. They caution that their analyses are highly dependent on assumptions about how effective the vaccines will be, levels of vaccine uptake, and how quickly the vaccine is rolled out. Due to the uncertainty surrounding such assumptions, it is important to monitor the impact of future relaxations by closely tracking data including infection prevalence, cases, hospitalisations, deaths, and studies monitoring potential variants of concern and quantifying the effectiveness of vaccination in different populations.