A recent study published in Nature Medicine sought to clinically assess asymptomatic COVID-19 patients. They conducted their study using 37 asymptomatic individuals. The study noted that virus specific IgG antibodies were significantly lower in asymptomatic patients than in the symptomatic group. This group also had lower levels of 18 pro- and anti- inflammatory cytokines. The asymptomatic group also has a longer duration of viral shedding time of 19 days.
8 weeks post discharge from the hospital, it was found that the IgG levels in the asymptomatic group were still lower than the symptomatic group. It is interesting to see that the IgG levels had declined in both groups. Additionally, there was also a decrease in neutralizing serum antibodies. Around 40% of asymptomatic individuals became seronegative for IgG whereas the percentage was much lower for symptomatic patients at 12.9%. Scientists note that the antibodies made in response to the infection may last only 2-3 months especially in asymptomatic individuals. This finding can have serious implications for easing or lifting social distancing measures as it is no longer safe to assume that previous infection by SARS-CoV-2 can protect against re-infection. It supports the extension of the various public health initiatives already at play like social distancing, maintain hygiene and more testing.
In the case of SARS and MERS, it was observed that the neutralizing antibodies lasted for at least a year and that IgG levels were maintained for 2 years after SARS-CoV infection. However, this does not appear to be the case with SARS-CoV-2. Thus, more studies are needed to determine how long antibody-mediated immunity lasts with SARS-CoV-2.
By: Sanya Bansal