Long-term and herd immunity against SARS-CoV-2: implications from current and past knowledge

Area of Science:

• Virology
• Immunology
• Epidemiology

Background:

• Herd immunity for SARS-CoV-2 depends on population immunity, immune response duration, and viral stability.
• Estimates suggest 50-66% population immunity is needed, which is slow to achieve via natural infection.
• Concerns exist regarding the duration and effectiveness of natural immunity, with reported relapses and emerging mutant strains.

Purpose of the Study:

• To evaluate the feasibility of achieving herd immunity for SARS-CoV-2 through natural infection.
• To highlight the challenges posed by viral evolution and immune response limitations.
• To underscore the urgent need for a SARS-CoV-2 vaccine.

Main Methods:

• Analysis of factors influencing herd immunity: population immunity percentage, immune response duration and effectiveness, and viral epitope stability.
• Review of existing data on SARS-CoV immunity and reported SARS-CoV-2 cases, including relapses.
• Consideration of the impact of emerging SARS-CoV-2 mutant strains.

Main Results:

• Natural achievement of herd immunity for SARS-CoV-2 is projected to be a lengthy process.
• The duration and effectiveness of natural immunity may be insufficient for sustained control.
• Viral mutations pose a significant risk for epidemic resurgence.

Conclusions:

• Natural herd immunity for SARS-CoV-2 is unlikely to be achieved promptly or be sufficiently robust.
• The development of an effective vaccine is critical for controlling current and future SARS-CoV-2 outbreaks.
• Vaccination is essential to overcome limitations of natural immunity and viral evolution.