Study on Continuation of Antibody Prevalence Six Months after Detection of Subclinical Severe Acute Respiratory Syndrome Coronavirus 2 Infections

OBJECTIVE: To examine the continuation of antibody prevalence and background factors in antibody-positive subjects after asymptomatic infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). METHODS: A study was carried out to investigate the SARS-CoV-2 antibody (IgG) prevalence. SARS-CoV-2 antibodies (IgG) were measured and analyzed with immunochromatographic tests. PATIENTS: Among 1,603 subjects, comprising patients, physicians, and nurses at 65 medical institutes in Kanagawa, Japan, 39 antibody-positive subjects received follow-up for 6 months. RESULTS: Of the 33 subjects who consented to the follow-up (23 patients and 10 medical professionals), continued positivity of IgG antibodies was confirmed in 11 of 32 cases (34.4%) after 2 months, 8 of 33 (24.2%) after 4 months, and 8 of 33 (24.2%) after 6 months. A significant difference was found in the sleeping time, drinking habits, hypertension, and use of angiotensin-receptor blockers on comparing subject background characteristics among three groups: patients with antibody production that continued for six months after the first detection of positivity, patients in whom antibody production stopped at four months, and patients in whom antibody production stopped at two months. CONCLUSION: The continuation rate of IgG antibody prevalence was 24.2% at 6 months after the first detection of antibody positivity in cases with asymptomatic coronavirus disease 2019 (COVID-19) infections. This percentage is low compared with the antibody continuation rate in patients who have recovered from symptomatic COVID-19 infection.