COVID-19 Tipsheet: COVID Immunity and Antibodies


Dr. Amira Roess is a professor of Global and Community Health at George Mason University’s College of Health and Human Services. She is an epidemiologist with expertise in Coronaviruses and interventions to reduce the transmission and impact of infectious diseases. Roess provides some insight on immunity to COVID-19 and antibodies.


What do we know about immunity after being diagnosed with Covid?

We are still learning about this for COVID-19. What we typically observe with other viruses is that once a person mounts a robust immune response, about 2 or more weeks after infection, then that person may be considered immune from the virus and not able to infect others for at least some time. Immunity wanes, or disappears, fairly quickly for coronaviruses.

How long does immunity last? And does it prevent reinfection and spread?

Right now, we estimate that a person with a baseline robust immune system may be immune for 90 or more days. Recent studies suggest that individuals who had more severe COVID-19 illness have strong antibody responses for up to 7 months, and that individuals who were asymptomatic or had mild symptoms may not have a strong immune response. The latter group may have a greater chance of getting reinfected and thus spreading the virus to others.  We are still learning about the COVID-19 virus. Among individuals who have weakened immune systems or who are on immunosuppressive treatments, we expect variation in this. I mention this because we have a greater number of individuals who fit this now than in the previous decades.

Is an antibody test different than a COVID-19 test that detects the active virus?

Yes. The antibody test looks for evidence of previous infection and usually requires venous blood samples.

If someone tests positive within their 90 days of immunity is this a false positive? Or is the test detecting the antibodies?

It depends on what test was in use. It is possible that following infection virus particles (that may or may not be infectious) can still be detected for a few weeks following initial infection or diagnosis.

About George Mason University

George Mason University is Virginia's largest and most diverse public research university. Located near Washington, D.C., Mason enrolls 39,000 students from 130 countries and all 50 states. Mason has grown rapidly over the past half-century and is recognized for its innovation and entrepreneurship, remarkable diversity and commitment to accessibility. For more information, visit

About the College of Health and Human Services

George Mason University's College of Health and Human Services prepares students to become leaders and shape the public's health through academic excellence, research of consequence, community outreach, and interprofessional clinical practice. George Mason is the fastest-growing Research I institution in the country. The College enrolls more than 1,900 undergraduate and 1,370 graduate students in its nationally-recognized offerings, including: 5 undergraduate degrees, 13 graduate degrees, and 7 certificate programs. The college is transitioning to a college of public health in the near future. For more information, visit