Can COVID-19 herd immunity be achieved at a city level?

Area of Science:

• Epidemiology
• Public Health
• Vaccinology

Background:

• The COVID-19 pandemic necessitates understanding herd immunity thresholds for effective control.
• Vaccination strategies are crucial for mitigating SARS-CoV-2 spread and its impact on urban populations.

Purpose of the Study:

• To estimate the vaccination rates needed to achieve herd immunity against SARS-CoV-2 at a city level.
• To model the relationship between vaccination rates and COVID-19 morbidity using quadratic models.

Main Methods:

• Utilized data from the Israeli Ministry of Health on the BNT162b2 mRNA Pfizer vaccine.
• Developed two quadratic models, one for each vaccine dose, with morbidity as the dependent variable.
• Independent variables included first and second vaccination rates and their squared values.

Main Results:

• Herd immunity is estimated to be achieved when 71% of the urban population is vaccinated.
• A vaccination rate of 71% is associated with approximately 5 active COVID-19 cases per 10,000 persons.
• This represents a significant reduction from 53-67 cases per 10,000 persons at a zero vaccination rate.

Conclusions:

• Vaccination is critical for achieving urban herd immunity against COVID-19.
• Urban herd immunity, characterized by contained spread during continued interaction, can prevent the need for city-level restrictions like lockdowns.