Critical weaknesses in shielding strategies for COVID-19

Area of Science:

• Epidemiology
• Public Health Modeling
• Infectious Disease Dynamics

Background:

• The COVID-19 pandemic necessitated widespread non-pharmaceutical interventions.
• Lockdowns imposed significant economic and social burdens.
• An alternative strategy proposed was 'shielding' vulnerable individuals while allowing herd immunity to develop in lower-risk groups.

Purpose of the Study:

• To retrospectively evaluate the effectiveness of a 'shielding' strategy for COVID-19.
• To model the impact of shielding on hospital capacity and mortality.
• To assess the viability of this strategy for current and future pandemics.

Main Methods:

• Utilized a stochastic SEIR (Susceptible-Exposed-Infectious-Recovered) framework.
• Simulated scenarios with varying degrees of shielding effectiveness.
• Analyzed outcomes including hospital overwhelm and excess mortality.

Main Results:

• Even with perfect shielding, hospital systems would have been overwhelmed.
• Significant avoidable deaths occurred among lower-risk individuals under shielding scenarios.
• A mere 20% reduction in shielding effectiveness drastically increased mortality (>150%).

Conclusions:

• The 'shielding' strategy is not a viable public health approach for COVID-19.
• This strategy would lead to overwhelmed healthcare systems and high mortality.
• The findings suggest limited applicability for shielding in future pandemic responses.