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How do we become immune to a disease?

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When germs enter your body, your immune system springs into action. Here's how it works:

  • Bacteria and viruses like the one that causes COVID-19 have proteins called antigens on their surfaces. Each type of germ has its own unique antigen.
  • White blood cells of your immune system make proteins called antibodies to fight the antigen. Antibodies attach to antigens the way a key fits into a lock, and they destroy the invading germ.
  • Once you've been exposed to a virus, your body makes memory cells. If you're exposed to that same virus again, these cells recognize it. They tell your immune system to make antibodies against it.

Vaccines work in much the same way. They expose your body to an antigen that trains your immune system to fight that germ in the future. Because vaccines contain weakened or killed versions of viruses, you become immune without getting sick.

SOURCES:

Children's Hospital of Philadelphia: "Types of Immunity."

FDA: "Coronavirus (COVID-19) Update: Serological Tests," "Coronavirus (COVID-19) Update: Serological Test Validation and Education Efforts."

Harvard Medical School: "If you've been exposed to the coronavirus."

Immunologic Research: "T cell-mediated immune response to respiratory coronaviruses."

Johns Hopkins Bloomberg School of Public Health: "What Is Herd Immunity and How Can We Achieve It With COVID-19?"

Johns Hopkins Center for Health Security: "Serology-based tests for COVID-19."

KidsHealth.org: "Immune System."

MD Anderson Cancer Center: "7 things to know about COVID-19 antibody testing."

Microbiology Society: "Antibody-antigen complex."

New England Journal of Medicine: "Asymptomatic Transmission, the Achilles' Heel of Current Strategies to Control Covid-19."

University of California San Francisco: "The Promise and Uncertainties of Antibody Testing for Coronavirus."

Vaccines.gov: "Vaccines Protect Your Community."

World Health Organization: "'Immunity passports' in the context of COVID-19."

Canadian Medical Association Journal:" COVID-19: Recent updates on the coronavirus pandemic."

National Institutes of Health: "NIH begins study to quantify undetected cases of coronavirus infection."

Reviewed by Brunilda Nazario on September 23, 2020

SOURCES:

Children's Hospital of Philadelphia: "Types of Immunity."

FDA: "Coronavirus (COVID-19) Update: Serological Tests," "Coronavirus (COVID-19) Update: Serological Test Validation and Education Efforts."

Harvard Medical School: "If you've been exposed to the coronavirus."

Immunologic Research: "T cell-mediated immune response to respiratory coronaviruses."

Johns Hopkins Bloomberg School of Public Health: "What Is Herd Immunity and How Can We Achieve It With COVID-19?"

Johns Hopkins Center for Health Security: "Serology-based tests for COVID-19."

KidsHealth.org: "Immune System."

MD Anderson Cancer Center: "7 things to know about COVID-19 antibody testing."

Microbiology Society: "Antibody-antigen complex."

New England Journal of Medicine: "Asymptomatic Transmission, the Achilles' Heel of Current Strategies to Control Covid-19."

University of California San Francisco: "The Promise and Uncertainties of Antibody Testing for Coronavirus."

Vaccines.gov: "Vaccines Protect Your Community."

World Health Organization: "'Immunity passports' in the context of COVID-19."

Canadian Medical Association Journal:" COVID-19: Recent updates on the coronavirus pandemic."

National Institutes of Health: "NIH begins study to quantify undetected cases of coronavirus infection."

Reviewed by Brunilda Nazario on September 23, 2020

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If you've had COVID-19, are you immune to it?

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