PIN20 Predicting the IMPACT of Vaccination Strategies in the COVID-19 Pandemic Using a Susceptible-Exposed-Infectious-Removed (SEIR) MODEL

ABSTRACT

Objectives: Coronavirus (COVID-19) has resulted in 84.53 million infections and 1.85 million deaths world-wide in 2020 and both numbers are still increasing. Using a Susceptible-Exposed-Infectious-Removed (SEIR) model, this study aimed to predict the impact of different vaccination strategies in the UK on mortality, productivity loss, and healthcare burden. Methods: A SEIR model was built in R using the UK estimated age-group specific proportions of asymptomatic infections, probability of severe symptoms and death rate from published literature. Assuming vaccine supply covers 20% or 50% of the UK population as two base scenarios, three population-wide vaccination strategies with different age group priorities were modelled. Total number of infections, COVID-19 related deaths, quality-adjusted life years (QALYs) lost, cost for critical and non-critical care, and productivity loss were estimated. Results: In the 20% population coverage scenario, 2 million more infections were prevented by vaccinating the 15-34 age group first, compared to vaccinating those over 65 first. A £6.6 billion reduction (13%) in direct healthcare costs was predicted by prioritising people over 65. Productivity and QALY losses were minimised by prioritising the 15-34 age group, while only vaccinating those over 65 resulted in the lowest number of deaths. Increasing population coverage from 20% to 50% resulted in drops in QALY loss and healthcare burden, but did not affect the age group strategy. A strategy that prioritises elderly vaccination would minimise QALY losses only if the death rate amongst 15-34s dropped by 17.4% (from 10.9% to 9%). Conclusions: With constraints in vaccine supplies, greater reductions in hospitalisation costs related to COVID-19 and deaths were associated with a vaccination strategy prioritising older age groups. Lower QALY and productivity losses were associated with a vaccination strategy prioritising younger cohorts. Future research adding age-group specific social distancing measures may provide further insights.