Tests on patients treated at Munich's Schwabing Clinic showed a significant drop in the number of so-called neutralizing antibodies in the blood, said Clemens Wendtner, senior consultant at the hospital's department for infectious diseases.
"In four of the nine patients, we see falling neutralizing antibodies in a very special test that can only be carried out in a high-security laboratory," Wendtner said.
"The extent to which this has an impact on long-term immunity and vaccination strategies is still speculative, but must be monitored critically as it progresses," The AAPn cited him as saying.
The results suggest that recovered patients can be re-infected with the virus, though further tests are necessary to confirm this, Wendtner said.
Wendtner's findings chime with other studies around the world.
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