COVID-19 Network Model to Evaluate Vaccine Strategies towards Herd Immunity

Abstract

AbstractWith more than 60 million confirmed cases and more than 1.5 million deaths, SARS-CoV-2 has paralyzed our societies, leading to self isolation and quarantine for several months. A COVID-19 vaccine remains a critical element in the eventual solution to this public health crisis. Two vaccines are ready to be mass produced and eventually supplied to the population. Here, we develop an epidemiological network model able to represent COVID-19 pandemic dynamics of different countries such as in Italy. Stochastic computational simulations identify the necessary number of vaccines and vaccine efficacy thresholds capable of preventing an epidemic whilst adhering to lockdown guidelines. Assuming a vaccine efficacy of 100% in a mass vaccination program, at least 60% of a given population should be vaccinated to obtain herd immunity. Otherwise, new waves of COVID-19 would be reported. However, reaching 60% of the population will be an unprecedented mass immunisation campaign that will take several months and millions of dollars. If the vaccine efficacy reports lower levels of efficacy in practice, then the coverage of vaccination would be needed to be even higher. Simulations suggest that the “Ring of Vaccination” strategy, vaccinating susceptible contact and contact of contacts, would be a more tractable vaccine strategy to prevent the new waves of COVID-19 meanwhile a high percent of the population is vaccinated.