Vaccination Against COVID-19 and Society's Return to Normality in England: A Modelling Study of Impacts of Different Types of Naturally Acquired and Vaccine Induced Immunity (preprint)

ObjectivesTo project impacts of mass vaccination against COVID-19, and investigate possible impacts of different types of naturally acquired and vaccine-induced immunity on future dynamics of SARS-CoV-2 transmission from 2021 to 2029 in England. DesignDeterministic, discrete-time population dynamic modelling. ParticipantsPopulation in England. Interventionsmass vaccination programmes. Outcome measuresdaily and cumulative number of deaths from COVID-19. ResultsIf vaccine efficacy is [≥] 70%, the vaccine-induced sterilising immunity lasts [≥] 182 days, and the reinfectivity is greatly reduced (by [≥] 40%), mass vaccination programmes can prevent further COVID-19 outbreaks in England. Under such optimistic scenarios, the cumulative number of COVID-19 deaths is estimated to be from 113,000 to 115,000 by the end of 2029 in England. However, under plausible scenarios with lower vaccine efficacy, shorter durability of immunity, and smaller reduction in reinfectivity, repeated vaccination programmes could not prevent further COVID-19 outbreaks. ConclusionsUnder optimistic scenarios, mass immunisation using efficacious vaccines may enable society safely to return to normality. However, under plausible scenarios with low vaccine efficacy and short durability of immunity, COVID-19 could continue to cause recurrent waves of severe morbidity and mortality despite frequent vaccinations. It is crucial to monitor the vaccination effects in the real world, and to better understand characteristics of naturally acquired and vaccine induced immunity against SARS-CoV-2. ARTICLE SUMMARYO_ST_ABSStrengths and limitations of this studyC_ST_ABSO_LIWe used a population dynamic model to assess impacts of vaccination programmes on future dynamics of SARS-CoV-2 transmission dynamics, and to explicitly investigate the impacts of different types of immune responses to SARS-CoV-2 infection and vaccines on the COVID-19 epidemic in England. C_LIO_LIThe model has been verified based on historically observed outcome data in England, and a large number of projection scenarios are explored. C_LIO_LIFindings from our study improves the understanding of key immunological parameters relevant to future SARS-CoV-2 transmission dynamics and vaccination strategies. C_LIO_LIThis is a deterministic simulation model, and uncertainty in estimated parameters may have not been fully accommodated. There remain many uncertainties regarding durability and types of naturally acquired and vaccine-induced immunity. C_LI