AsianScientist (Jun. 19, 2020) – Asymptomatic COVID-19 patients may have a weaker immune response to the SARS-CoV-2 virus, suggests a study published in Nature Medicine this week. These findings highlight the potential risks of using ‘immunity passports’ to identify people with antibodies against the virus.
The strength and duration of immunity after COVID-19 infection are key for informing decisions on how and when to ease physical distancing restrictions. Previous studies have shown that circulating antibodies against SARS-CoV or MERS-CoV last for at least one year, while sustained IgG levels were maintained for more than two years after SARS-CoV infection.
To better understand the profile of asymptomatic COVID-19 patients, Qiu Jing-Fu, Chen Juan, Huang Ai-Long and colleagues at Chongqing Medical University carried out a detailed clinical and immunological analysis of 37 asymptomatic patients infected with the SARS-CoV-2 virus from the Wanzhou district of Chongqing, China.
Of the 37 asymptomatic patients—identified in a group of 178 people with SARS-CoV-2 infection—22 were female and 15 male, with ages ranging from 8 to 75 years (median age, 41 years). The authors found that these patients had a median duration of viral shedding of 19 days, compared with 14 days in a group of 37 symptomatic patients. Levels of virus-specific IgG antibodies were significantly lower in the asymptomatic group than in the symptomatic group during the acute phase of infection, when the virus could be detected in the respiratory tract.
Eight weeks after the patients were discharged from the hospital, levels of neutralizing antibodies decreased in 81.1 percent of asymptomatic patients, compared with 62.2 percent of symptomatic patients. In addition, asymptomatic patients had lower levels of 18 pro- and anti-inflammatory cytokines, which indicates that the asymptomatic patients may have had a weaker immune response to SARS-CoV-2 infection.
“In this study, we observed that IgG levels and neutralizing antibodies in a high proportion of individuals who recovered from SARS-CoV-2 infection start to decrease within two to three months after infection,” the authors write.
The data suggest the potential risks of using ‘immunity passports’ to mark people who have developed antibodies to the disease, and supports the continuation of public-health interventions, including social distancing, hygiene, isolation of high-risk groups and widespread testing, the authors suggest.
At the same time, longitudinal serological studies of larger groups of symptomatic and asymptomatic patients are urgently needed to determine the duration of antibody-based immunity, they add.
The article can be found at: Long et al. (2020) Clinical and Immunological Assessment of Asymptomatic SARS-CoV-2 Infections.
Source: Nature; Photo: United Nations COVID-19 Response/Unsplash.
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