Increasing detection of reinfections and rediscovering brand new infections within days raises concerns for herd immunity and the durability of vaccine efficacy.

Cynthia Tang
Cynthia Tang working to figure out how COVID-19 reinfections can bring us answers on how the virus is developing at Bond LSC. | photo by Davis Suppes, Bond LSC

By Davis Suppes | Bond LSC

 Like many viruses, SARS-CoV-2 continues to develop and evolve with time. As the virus evolves it becomes more infectious and can produce worse symptoms and a higher fatality rate. While more people have been infected, we also learn more about it, including how different variants of the same virus can reinfect someone who already had SARS-CoV-2.

In a recent study led by Cynthia Tang, an MD-PhD student at the University of Missouri (MU) School of Medicine and Institute for Data Science and Informatics, her lab was able to identify a patient who got reinfected with a different strain of SARS-CoV-2 just 19 days after their initial infection. Her Systems Biology Laboratory is headed by Principal Investigator, Dr. Henry Wan, who directs the MU Center for Influenza and Emerging infectious Diseases.

“We found a case of reinfection that occurred during a shorter window of time than what we see in the current US Centers for Disease Control and Prevention (CDC) guidelines,” Tang said, “so we may be missing a subset of those reinfection cases.”

In October 2020, the CDC published investigative criteria for suspected SARS-CoV-2 reinfections. These criteria included: any individuals testing positive over 90 days after their first laboratory-confirmed SARS-CoV-2 infection, or symptomatic individuals testing positive 45–89 days after initial infection with paired respiratory specimens.

For this patient, nineteen days following her initial positive test in March of 2020, she returned for another SARS-CoV-2 test due to return-to-work requirements. Despite her symptoms fading to encompass only productive cough and fatigue she tested positive again. She continued to experience persistent cough, fatigue, and difficulty breathing until 55 days after her initial positive test.

Tang showed that the two samples contained two infectious variants of SARS-CoV-2 viruses. No diverse polymorphisms, or a mixture of different viruses, were identified among the sequences of the viruses from each clinical sample, suggesting true reinfection rather than a coinfection. One good news is that this case also suggests that reinfections may not be worse than the prior infection.

The CDC has encouraged symptom-based strategies for ending isolation rather than viral retesting for asymptomatic individuals or for individuals without new symptoms during 90 days after illness onset due to findings that detectable but noninfectious SARS-CoV-2 RNA can persist in respiratory samples. This means that even if you don’t exhibit symptoms there could still be traces of SARS-CoV-2 in your system, and those traces could be from an original infection or a reinfection.

This study suggested that reinfection could pose a challenge to infection control, especially as the Delta variants are surging around and new variants continue to emerge.

“People showing influenza-like illnesses are recommended to isolate themselves for ten days or wait for their symptoms to go away. We may not be catching cases where individuals contract another COVID-19 infection within a short amount of time,” Tang said.

“The COVID-19 vaccination has been proven to be effective in reducing the chances for people to become infected and reinfected”, Tang added.

This research was published in the Journal of Medical Virology in June 2021.