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Can someone be infected with COVID-19 more than once? | Covid-19 Expert Database Can someone be infected with COVID-19 more than once? | Covid-19 Expert Database

COVID-19 Expert Database


Can someone be infected with COVID-19 more than once?

Last modified on 30 August 2020

What our experts say

We are still learning a lot about what kind of natural defense, also known as immunity, a person has after being infected with SARS-CoV-2/COVID-19. A very small amount of people have reportedly become reinfected with virus following an initial infection.

Regardless of the anecdotal evidence, scientists still do not know for sure if people can become infected with COVID-19 a second time, but it appears to be possible. More evidence is needed to determine whether or not reinfection can occur in patients, how common it is, and what kind of immunity to the virus people might obtain once they have been infected.

Recent pre-print studies cite apparent cases of COVID-19 reinfecting patients, but those findings have not yet been published or peer-reviewed, so other scientific experts are not yet able to rigorously study the data or full results of the papers. It should be noted that the patients in the studies were supposedly infected with different strains of the virus during their second infection. This might mean that patients do not have lifelong immunity to the virus, and if any immunity does exist after someone is infected, the length and strength of the immunity is unclear.

In some cases of patients testing positive a second time, scientists think that traces of the original infection left in the body are cause the second positive result. This could be due to very sensitive tests or false-positive tests.

It is also important to note that antibody levels may not be a strong indicator of immunity against the virus and susceptibility to reinfection.

This entry was updated with new information on August 30, 2020

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Context and background

As scientists, public health professionals, and doctors monitor the COVID-19 pandemic, they continue to learn about how the virus spreads, its symptoms, and other factors important to diagnosis, testing, monitoring, and long-term public health planning. The possibility of reinfection continues to be a prominent news headline with healthcare professionals reporting that some patients who had fully recovered from the virus later redeveloped symptoms. Some case reports detail how both symptom monitoring and testing have been performed, and, in some instances, patients have documented recovery of COVID-19 with negative virus test results only to become ill and test positive weeks or months later. 

While there are still many aspects of the virus and the pandemic that are unknown, recent research suggests that reinfection may be possible. Newer research shared with a preprint release on July 11th, 2020 found that COVID-19 antibodies function similarly to those from other coronaviruses that are associated with common colds. While the number of antibodies is higher in patients with more severe illness, reports suggest that the protective antibodies decrease relatively quickly (sometimes within 60 days), especially in patients who had a mild case of COVID-19. Similarly, a population-based study from Spain examined antibodies of more than 50,000 people with possible exposure early in the pandemic and found that very few people have maintained antibodies to date, even those who lived in areas significantly impacted by the virus. Finally, a study done in primates (not humans) showed that COVID-19 immunity was maintained for 28 days following the original infection, but the study did not include longer range measures and, as an animal study, may not be directly comparable to humans.

It is important to note that, unlike other viruses, the number of antibodies needed to prevent reinfection with COVID-19 is unknown as is the level of antibodies needed to suggest that someone is “immune” to the virus. Studies to further understand immunity as well as the possibility for reinfection are ongoing.


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  1. Longitudinal evaluation and decline of antibody responses in SARS-CoV-2 infection (MedRxiv)
  2. Direct observation of repeated infections with endemic coronaviruses (J of Inf Disease)
  3. Prevalence of SARS-CoV-2 in Spain (ENE-COVID): a nationwide, population-based seroepidemiological study (Lancet)
  4. Study in Primates Finds Acquired Immunity Prevents COVID-19 Reinfections (NIH Director’s Blog)
  5. Interview with Virologist Dr. Rasmussen (Gizmodo)
  6. What Is COVID-19? (JAMA)
  7. Scientists say Hong Kong man got coronavirus a second time (AP)
  8. First Documented Coronavirus Reinfection Reported in Hong Kong (NYT)
  9. Genomic Evidence for a Case of Reinfection with SARS-CoV-2 (The Lancet Preprint)
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