IF YOU ARE FULLY VACCINATED
CDC has updated its guidance for people who are fully vaccinated. See Recommendations for Fully Vaccinated People.
IMPORTANT UPDATE FOR SCHOOLS
CDC recommends schools continue to use the current COVID-19 prevention strategies for the 2020-2021 school year. Learn more
Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
UPDATE
Getting vaccinated prevents severe illness, hospitalizations, and death. Unvaccinated people should get vaccinated and continue masking until they are fully vaccinated. With the Delta variant, this is more urgent than ever. CDC has updated guidance for fully vaccinated people based on new evidence on the Delta variant.
UPDATE
Given new evidence on the B.1.617.2 (Delta) variant, CDC has updated the guidance for fully vaccinated people. CDC recommends universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status. Children should return to full-time in-person learning in the fall with layered prevention strategies in place.

What COVID-19 Seroprevalence Surveys Can Tell Us

What COVID-19 Seroprevalence Surveys Can Tell Us
Updated July 8, 2020

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Infographic: A seroprevalence survey uses antibody tests to estimate the percentage of people in a population who have antibodies against SARS-CoV-2. This page includes a graphic explaining how seroprevlance surveys use antibody test to measure the percent of a population likely have a past infections with SARS-CoV-2, the virus that causes COVID-19.

What COVID-19 Seroprevalence Surveys Can Tell Us

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)

Seroprevalence

The percentage of individuals in a population who have antibodies to an infectious agent is called seroprevalence.

Seroprevalence Survey

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).