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

Background: Past infection with COVID-19 or vaccination against SARS-CoV-2 may induce immune responses that prevent infection (sterilising immunity), reduce disease severity and infectivity after being reinfected. Methods: We developed a deterministic, discrete-time population dynamic model to assess impacts of vaccination programmes on future dynamics of SARS-CoV-2 transmission in England. The model explicitly considered durability and different types of naturally acquired and vaccine-induced immunity against SARS-CoV-2 and their impacts on COVID-19 transmission dynamics from 2020 to 2029 in England. We explored a large number of projection scenarios. Findings: If vaccine efficacy is ≥70%, the vaccine-induced sterilising immunity lasts ≥182 days on average, and the reinfectivity is greatly reduced (by ≥40%), annual 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. Interpretations: Because of great uncertainty in the impacts of mass vaccination on COVID-19 pandemics, it is crucial to monitor vaccination effects in the real world, and to better understand characteristics of naturally acquired and vaccine induced immunity against SARS-CoV-2. Funding: No specific funding received for this study. Declaration of Interests: No competing interests declared.