Vaccination and SARS-CoV-2 variants: how much containment is still needed? A quantitative assessment (2102.08704v1)

Abstract: Despite the progress in medical care, combined population-wide interventions (such as physical distancing, testing and contact tracing) are still crucial to manage the SARS-CoV-2 pandemic, aggravated by the emergence of new highly transmissible variants. We combine the compartmental SIDARTHE model, predicting the course of COVID-19 infections, with a new data-based model that projects new cases onto casualties and healthcare system costs. Based on the Italian case study, we outline several scenarios: mass vaccination campaigns with different paces, different transmission rates due to new variants, and different enforced countermeasures, including the alternation of opening and closure phases. Our results demonstrate that non-pharmaceutical interventions (NPIs) have a higher impact on the epidemic evolution than vaccination, which advocates for the need to keep containment measures in place throughout the vaccination campaign. We also show that, if intermittent open-close strategies are adopted, deaths and healthcare system costs can be drastically reduced, without any aggravation of socioeconomic losses, as long as one has the foresight to start with a closing phase rather than an opening one.

Quantitative Assessment of Vaccine Strategies and SARS-CoV-2 Variants

This paper presents a robust quantitative evaluation of vaccination strategies and their interaction with non-pharmaceutical interventions (NPIs) in managing the spread of SARS-CoV-2, especially amidst the emergence of more transmissible variants. Utilizing a comprehensive modeling framework that extends the SIDARTHE model to incorporate vaccination effects, the paper evaluates various scenarios based on vaccination speed, transmission rates driven by variants, and strategies involving alternating open-close phases.

Central to the findings is the assertion that NPIs play a significantly more critical role than vaccination speed in controlling the epidemic trajectory. The paper highlights that maintaining restrictive measures through mass vaccination campaigns is necessary, especially with highly transmissible variants in circulation. Rapid relaxation of these measures could lead to surges in infection cases, compelling further closures, which could trigger repeated cycles of intermittent restrictions.

The paper evaluates twenty distinct scenarios by systematically varying the pace of vaccination and profiles of the reproduction number (Ro). Each scenario is analyzed for its impact on deaths and healthcare costs—two critical metrics for public health policy formulation. This simulation reveals that, except for an unrealistic eradication scenario, all other profiles demonstrate significant life-saving potential through vaccination, with mid-to-fast schedules averting up to 57% more deaths versus no vaccination.

The analysis also posits that NPIs drastically reduce sensitivity to vaccination delays, underlining their five-fold impact on mortality compared to vaccination pace. Moreover, pre-emptive strategies—initiating restrictions before peak case numbers—prove more effective in reducing deaths and healthcare burdens without additional socioeconomic costs. These findings advocate for the anticipation of closing phases within open-close strategies to optimally manage the epidemic curve.

The paper anticipates further theoretical exploration of its models and practical implications in near-future research. The implications for COVID-19 look beyond vaccines, indicating a strong reliance on behavioral interventions to mitigate healthcare burdens effectively. As vaccines progressively reach broader segments of the population, their interaction with evolving virus variants should continue to guide adaptive public health strategies.

In summary, the paper underscores the indispensability of coordinated public health interventions alongside vaccination campaigns, emphasizing that containment measures should remain robustly enforced until population-level immunity is achieved. The future direction of such research will likely explore adaptive models that respond dynamically to shifting epidemic landscapes and emerging viral mutations.