Recently, an increasing amount of COVID-19 reinfection claims around the world have been begging the question of whether one is immune to the deadly virus after recovery.
The jury, however, is still out, with multiple inconclusive reports creating ambiguity – especially as nations start considering when to lift lockdown regulations.
South Korea incident
Several days ago, alarming positive retest results from Korea have been reported. After being released from quarantine, 51 South Koreans retested positive for COVID-19.
However, authorities are still deliberating whether the patients did fully recover and then were later reinfected with the virus – or whether they never, in fact, completely recovered from the initial contraction.
A new preprint China study suggests that recovered patients may not have protective antibodies. In the study – made available by medRxiv and authored by researchers of the School of Basic Medical Sciences at Fudan University in Shanghai – the scientists examined blood samples from over 150 patients from the city. The patients tested only experienced a mild form of COVID-19.
While the study has yet to be peer-reviewed by external experts and accepted for publication in a scientific journal, it found that almost a third of those who recovered had low levels of neutralizing antibodies (NAbs) against COVID-19. Ten patients within the study displayed no detectable level of NAbs.
NAbs are antibodies produced against viruses and bacteria when the body responds to infection. The antibodies defend a cell from infectious bacteria by neutralizing any effect it has biologically and can persist in an individual’s system for years and sometimes, decades. The antibodies can either be natural or artificial (e.g. vaccinations).
“About 30% of recovered patients generated very low titers of SARS-CoV-2-specific NAbs,” the report reads. The patients were divided into three age groups (15-39, 40-59 and 60-85) and it was found that elderly and middle-age recovered COVID-19 patients developed higher levels of SARS-CoV-2-specific NAbs compared to the younger patients.
The study claims to be the first systematic research of the antibody levels of patients who have recovered from COVID-19.