Antibodies could disappear after 2 months in the COVID recovered individuals

July 24, 2020 0 By FM

Patients who develop antibodies after becoming infected with COVID do not keep them more than a few months, especially in asymptomatic cases, found a Chinese study.

The study evaluated the clinical features and immune responses including 37 asymptomatic individuals in the Wanzhou District, China. The patients were diagnosed with RT–PCR-confirmed SARS-CoV-2 infections but without any relevant clinical symptoms in the preceding 14 days and during hospitalization.

According to the study, after eight weeks from recovery, the antibody levels fell to undetectable levels in 40% of the asymptomatic people while 12.9% of symptomatic people also became seronegative by this time.

The researchers tested for two types of antibodies: immunoglobulin G (IgG) and immunoglobulin M (IgM). IgG usually develops over a longer time period, meaning it’s a better indicator of long-term immunity. The virus-specific IgG levels in the asymptomatic group were significantly lower relative to the symptomatic group in the acute phase.

Of asymptomatic individuals, 93.3% (28/30) and 81.1% (30/37) had a reduction in IgG and neutralizing antibody levels, respectively, during the early convalescent phase, as compared to 96.8% (30/31) and 62.2% (23/37) of symptomatic patients.

The decrease in detectable antibodies was sharp after 8 weeks, with a 71% median drop for IgG levels in the asymptomatic group and a 76% median drop in the symptomatic group, the study said.

 The researchers noted that only a small group of people were studied and that the human body can also use T cells to kill the virus and B cells to produce new antibodies. Neither T cells nor B cells were measured in the new study.   

The study also stressed that the asymptomatic group had a significantly longer duration of viral shedding than the symptomatic group, highlighting the importance of maintaining social distancing and hygiene measures. In addition, asymptomatic individuals exhibited lower levels of 18 pro- and anti-inflammatory cytokines, suggesting a weaker immune response.

The study is published online in the journal Nature Medicine.