Antibodies may be undetectable in some recovered mild COVID-19 patients

Antibodies may be undetectable in some recovered mild COVID-19 patients

Last Reviewed : 12/23/2020
Antibodies may be undetectable in some recovered mild COVID-19 patients

Individuals infected by viral illnesses develop antibodies specific to the virus causing infection. These antibodies help to prevent reinfection by the same virus. With certain viruses like chickenpox, infected individual develops lifelong immunity. SARS coronavirus produces antibodies that protect an affected individual from reinfection for about two years. It is unclear for how long individuals affected by COVID-19 will have immunity from reinfection.

A study that is not peer-reviewed yet collected blood samples from 175 COVID-19 recovered patients. All these patients had mild COVID-19 infection. Among these 175 patients, 30% patients had very low levels of antibodies and ten patients (6%) had antibodies that were under the detectable level. These ten patients had undetectable levels even after repeating the levels two weeks later. Patients who had high level of antibodies peaked at roughly 10-15 days after the onset of symptoms. Elderly and middle-aged patients had significantly higher antibodies than young patients.

The researchers concluded, "These results revealed that a proportion of patients infected with SARS-CoV-2 would recover without developing high titers of virus-specific [neutralizing antibodies]. How these patients recovered without the help of [antibodies] and whether they were at risk of reinfection of SARS-CoV-2 should be further explored."

This study raises concerns that people who had mild COVID-19 infection may not develop enough immunity to fight against reinfection. Further studies may be needed to validate this data, especially as this study is not peer-reviewed yet. Nonetheless, people who developed only mild infection should beware of reinfection. They should continue to take precautionary measures like social distancing, wearing face mask and regular hand washing.



  1. Fan Wu et al. Neutralizing antibody responses to SARS-CoV-2 in a COVID-19 recovered patient cohort and their implications. medRxiv 2020.03.30.20047365; doi:

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