As highly transmissible variants of the virus continue to spread, containment measures remain crucial to control the epidemic despite the vaccination campaign: more severe restrictions are way more effective in reducing the virus transmission than faster vaccination. Since the loosening of restrictions leads to a surge of infections and deaths, requiring even more severe restrictions, we end up in repeating cycles of lockdowns and reopenings: but, with equally long opening and closing periods, a preventive strategy significantly reduces hospitalizations and deaths compared to a late intervention, without aggravating socio-economic costs. These are the conclusions of an epidemiological modelling study, coordinated by the University of Trento and published in Nature Medicine, which examined the two crucial factors that are changing the pandemic scenario: the new, more contagious variants of Sars-CoV-2 and the availability of effective vaccines.
"We describe the evolution of the Covid-19 epidemic using the Sidarthe model, that we proposed in our previous article published in Nature Medicine a year ago. We extended the model to include the impact of vaccination", explains Giulia Giordano (corresponding author, Department of Industrial Engineering, University of Trento). "The Sidarthe model transmits the new daily cases of infection to a second dynamic model, based on epidemic data in Italy, which computes a profile of the resulting healthcare costs in terms of deaths and hospital and ICU occupancy".
The study compares different evolution scenarios of the epidemic in Italy, considering different paces of the vaccination campaign, the contagiousness of the virus associated with the new variants and the stringency of restrictions, including intermittent closings and reopenings. Vaccination always has a lower effect on the evolution of the epidemic than restrictions, which can contain the epidemic even without vaccination and which, even in the first phase of the vaccination campaign, are essential to reduce health costs and deaths.
"The effect we observed when we prepared the first draft of the work, in February, was really impressive: we could clearly see that more severe restrictions saved hundreds of thousands of lives, while the vaccination campaign had a lower, but fast, impact", says Giulia Giordano. "In the past months, many people were vaccinated and the tightening of restrictions has reduced the circulation of the virus, so now the gap between worst and best case has narrowed. However, given that immunity (in people who have been infected with Covid-19 or who have received the vaccine) can last for less than one year, to keep the infection under control, it will be essential keep safety and hygiene measures in place and use personal protective equipment, while continuing to monitor the epidemic with tests and contact tracing, to promptly tackle any outbreaks that may occur even after the vaccination campaign".
The results of the study underline the need to maintain sufficiently stringent restrictions in place even during the vaccination campaign, at least until the most vulnerable will have been vaccinated. The study also established that it is important to plan restrictions in advance: in a cycle of closures and opening of the same duration, starting with a closure, rather than an opening, saves tens of thousands of lives and considerably reduces healthcare costs, while socio-economic costs stay the same because only depend on the duration of the lockdown periods.
About the article
The article "Modelling vaccination rollouts, SARS-CoV-2 variants and the requirement for non-pharmaceutical interventions in Italy" was published on 16 April 2021 in "Nature Medicine" and is available in Open Access. The preprint version appeared on 17 February 2021 on arXiv: https://arxiv.org/abs/2102.08704
The first and corresponding author is Giulia Giordano (Department of Industrial Engineering, University of Trento) and the work is the result of a precious collaboration with Marta Colaneri (Fondazione Irccs Policlinico San Matteo, Pavia), Alessandro Di Filippo (Fondazione Irccs Policlinico San Matteo, Pavia), Franco Blanchini (University of Udine), Paolo Bolzern (Polytechnic University of Milan), Giuseppe De Nicolao (University of Pavia), Paolo Sacchi (Fondazione Irccs Policlinico San Matteo, Pavia), Patrizio Colaneri (Polytechnic University of Milan) and Raffaele Bruno (Fondazione Irccs Policlinico San Matteo and University of Pavia).
The article, published in "Nature Medicine", is available in Open Access (DOI: 10.1038 / s41591-021-01334-5) https://www.nature.com/articles/s41591-021-01334-5