COVID-19 patients testing positive for second infection not contagious, study shows

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Researchers in Korea found evidence that patients who test positive for COVID-19 a second time aren’t capable of infecting others, and may have neutralizing antibodies that protect them from getting sick again.

The findings from the Korean Centers for Disease Control and Prevention (KCDC) could have major ramifications for areas looking to reopen their economies, and have led health authorities in the nation to change their protocols for people who have been discharged from isolation.

Researchers studied 285 patients who had survived COVID-19, but subsequently tested positive after multiple negative tests showed they had supposedly recovered. The scientists found a total of 790 contacts, none of whom tested positive as a result of being exposed to the “reinfected” patients. 

In addition, virus samples collected from the reinfected patients couldn’t be grown in culture, meaning the patients were “shedding” dead virus particles.

In all re-positive cases and newly confirmed cases, researchers found neutralizing antibodies.

As a result of the findings, the KCDC said it is lifting the requirements that people need to  have a negative test result to return to work or school after recovering from a COVID-19 infection. 

Under the new protocols, no additional tests are required for patients who have been discharged from isolation.

The findings are potentially important as states and local governments in the U.S. begin to reopen their economies, and debate what safety standards will be needed. 

The results could also give new insight into the debate over immunity and antibody tests. Leaders are also leaning heavily on the tests to make policy decisions when the science around coronavirus immunity is still unclear. 

It is not known yet whether a positive result for antibodies means a person is immune to the disease, and experts have cautioned against making major decisions based on the test results.  

Experts believe the presence of antibodies probably means people have been exposed and have some level of protection against the virus, but they don’t have solid proof yet. They also don’t know how long immunity might last. 

The KCDC study showed that, despite antibodies, 44 percent of the “reinfected” population had symptoms such as a cough or sore throat.

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