[Solidarity, covid-19 and a lever without fulcrum.]

Area of Science:

• Epidemiology
• Public Health
• Infectious Disease Dynamics

Background:

• Herd immunity, or collective immunity, has been a central concept throughout the COVID-19 pandemic.
• It is often oversimplified as an 'epidemic end' achieved at a specific immunization threshold.
• Current pandemic dynamics with new variants and vaccine efficacy show this simplistic threshold is unattainable.

Purpose of the Study:

• To clarify the concept of collective immunity beyond a simple threshold.
• To highlight the role of vaccination and societal solidarity in achieving effective collective immunity.
• To address the solidarity deficit impacting pandemic control.

Main Methods:

• Analysis of pandemic development in relation to transmissibility of variants and vaccine effectiveness.
• Evaluation of the impact of containment measures (physical distancing, masks) and vaccination on epidemic progression.
• Assessment of societal solidarity at national and international levels.

Main Results:

• A critical threshold for herd immunity, as traditionally defined, is not reachable with current COVID-19 variants and vaccines.
• Effective collective immunity, acting as a brake on epidemic spread, is attainable and strengthens with higher vaccination coverage.
• A significant solidarity deficit exists, evidenced by delayed interventions and vaccine inequity between high and low-income countries.

Conclusions:

• Achieving effective collective immunity relies on sustained vaccination and adherence to public health measures, reflecting civic solidarity.
• Governmental and health authority actions require public support (civic solidarity) to be effective against epidemics.
• Individual and collective citizen participation is essential for building the necessary societal solidarity to combat pandemics.