There is documented evidence of reinfection with SARS-CoV-2. While getting sick with the virus might help us gain some immunity from another COVID-19 infection, it is unknown how long that immunity lasts.

People who have been infected with SARS-CoV-2 can potentially get infected within a few months. Reinfection and its severity also depend on individual susceptibility. Studies on unvaccinated people becoming infected with the alpha and beta variants found that typically less than 2% of study subjects who had previously tested positive for COVID-19 were reinfected. Now, however, with more research and more transmissible variants, researchers estimate that if not vaccinated, there is about a 50% risk of reinfection within 17 months. Vaccines reduce this risk significantly.

In one study, people unvaccinated against COVID-19 who got reinfected were compared to vaccinated individuals who also got reinfected. The study found that unvaccinated people were more than twice as likely to get reinfected when compared to vaccinated individuals. Health organizations worldwide highly recommend that everyone who is eligible get vaccinated against COVID-19 regardless of whether they have already been infected with SARS-CoV-2.

While the viral load of COVID appears to peak in the first week of illness, viral shedding from the upper respiratory tract has occurred up to 83 days later.

There is also documented evidence of what is known as reactivation of COVID-19 – a re-detectable positive COVID-19 viral RNA in a recovered patient that occurs within the first 4 weeks after previous infection. Reactivation is also known as relapse. Reactivation essentially occurs when a person who appears to have recovered from a virus still has small amounts of dormant virus in their body that becomes active again and can reactivate symptoms. In this case there is a continuation of the same original infection, meaning it is not a true reinfection.

Differentiating reactivation from reinfection is difficult because scientists can only truly identify reactivation if patients give samples during their first episode of illness, which are then kept and sequenced genetically. Because these types of  tests are not often done it’s difficult to know how common COVID-19 reactivation is. However, one May 2021 study found that in a small sample of people, 27% experienced reactivation.

Separate from reinfection and reactivation is prolonged viral shedding, though they are often confused. The process of virus shedding begins when you are infected with a virus. When infected with a virus, the cells in your body that host the infection release infectious virus particles that are then “shed” into the environment. Viral shedding of COVID-19 typically peaks in the first week of illness.

In the case of COVID-19, the definition of viral shedding has been broadened to include the shedding of viral genetic material (RNA), which aren’t necessarily infectious as fragments on their own. This type of shedding typically lasts up to 17 days, but has also been found to be able to last for more than 80 days in the upper respiratory tract, and over 120 days in the stool.

This type of prolonged shedding does not count as reinfection because it is not a new exposure infecting a person distinctly from a first one, and it is not reactivation because the virus fragments are not making the person sick (i.e. “reactivating” symptoms).

There have been some claims that those that get infected with SARS-CoV-2 once do not get reinfected. This information is not true. The CDC and several scientific publications have shared information on the possibility of reinfection. A study conducted between 2020 and 2021 among people who were reinfected found that those who were unvaccinated against COVID-19 had significantly higher chances of getting reinfected, as compared to those who got vaccinated.

There have also been claims that people can carry a “dead” virus. People can carry a dormant virus that could potentially later become reactivated, and can carry viral genetic material (RNA) that is a fragment of the virus and non-infectious (some experts call this a dead virus or fragments of a dead virus).

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