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When does a community reach the state of herd immunity?

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When a population reaches a state of herd immunity depends on the disease’s reproduction number, or R0. The R0 tells you the average number of people that a single person with the virus can infect if those people aren’t already immune. The higher the R0, the more people need to be resistant to reach herd immunity.

From: What Is Herd Immunity? WebMD Medical Reference

SOURCES:

CDC: “Vaccines and Immunizations: Glossary,” “Frequently Asked Questions -- Coronavirus Disease 2019 Basics,” “Understanding How Vaccines Work,” “Polio Elimination in the United States.”

Science Media Centre: “Expert Comments About Herd Immunity.”

Association for Professionals in Infection Control and Epidemiology: “Herd Immunity.”

John Hopkins Medicine: “The Immune System.”

mBio : “High Zika Virus Seroprevalence in Salvador, Northeastern Brazil Limits the Potential for Further Outbreaks.”

Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene & Tropical Medicine: “Critical Immunity Thresholds for Measles Elimination.”

Journal of Travel Medicine : “The reproductive number of COVID-19 is higher compared to SARS coronavirus.”

National Institutes of Health: “NIH clinical trial of investigational vaccine for COVID-19 begins.”

Imperial College London: “Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand.”

Journal of Medical Virology : “Coronavirus infections and immune responses.”

Reviewed by Arefa Cassoobhoy on March 23, 2020

SOURCES:

CDC: “Vaccines and Immunizations: Glossary,” “Frequently Asked Questions -- Coronavirus Disease 2019 Basics,” “Understanding How Vaccines Work,” “Polio Elimination in the United States.”

Science Media Centre: “Expert Comments About Herd Immunity.”

Association for Professionals in Infection Control and Epidemiology: “Herd Immunity.”

John Hopkins Medicine: “The Immune System.”

mBio : “High Zika Virus Seroprevalence in Salvador, Northeastern Brazil Limits the Potential for Further Outbreaks.”

Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene & Tropical Medicine: “Critical Immunity Thresholds for Measles Elimination.”

Journal of Travel Medicine : “The reproductive number of COVID-19 is higher compared to SARS coronavirus.”

National Institutes of Health: “NIH clinical trial of investigational vaccine for COVID-19 begins.”

Imperial College London: “Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand.”

Journal of Medical Virology : “Coronavirus infections and immune responses.”

Reviewed by Arefa Cassoobhoy on March 23, 2020

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