What COVID-19 Seroprevalence Surveys Can Tell Us
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Antibody against SARS-CoV-2
Serology, or antibody, testing checks a sample of a person’s blood to look for antibodies against SARS-CoV-2, the virus that causes COVID-19. Antibodies usually become detectable in the blood 1-3 weeks after someone is infected.
Person infected → 1-3 weeks → person has detectable level of antibodies*
*Some people may take longer than 3 weeks to develop antibodies, and some people may not develop antibodies. It is currently unknown how long antibodies are detectable after infection.
A positive result from this test may mean that a person was previously infected with the virus.
Positive (sample positive for SARS-CoV-2 antibodies)
Negative (Sample negative for SARS-CoV-2 antibodies)
The percentage of individuals in a population who have antibodies to an infectious agent is called seroprevalence.
A seroprevalence survey uses antibody tests to estimate the percentage of people in a population who have antibodies against SARS-CoV-2.
This can tell us how many people in a specific population may have been previously infected with SARS-CoV-2.
A small sample of people participating in the survey represents a larger population, which could be a community, state, or special population (like healthcare workers or pregnant people).