Background: To clarify the role of serum antibody in respiratory syncytial virus (RSV) reinfection, the authors conducted a follow-up study of patients with primary RSV infection.
Methods: From 1994 to 1995, 256 patients were a diagnosed with primary RSV infection based on the antigen detection in nasopharyngeal secretions using enzyme linked immunoassay method. One hundred and sixty-five patients were followed-up for 1 year, and 87 of the 165 patients showed respiratory symptoms in winter. When a patient had a symptom such as cough, wheezing, rhinorrhea or fever, the nasopharyngial secretion was examined for the presence of RSV. Forty-one patients (group 1) were diagnosed with reinfection with RSV and the other 46 patients (group 2) were not diagnosed with reinfection. The authors compared clinical features between primary infection and reinfection of group 1 and serum neutralization test (NT) antibody titers to RSV between group 1 and 2.
Results: The mean age was 6.0 +/- 3.6 months at RSV primary infection and 14.6 +/- 8.2 months at RSV reinfection. Hospitalization, oxygen supplementation, and use of respirator were required by 71%, 39%, 2%, respectively, in primary infection, and by 22%, 0%, 0%, respectively, in reinfection. All children in group 1 had titers of 1 : 16 or lower, while 39.1% of children in group 2 had titers of 1 : 16 or lower (P < 0.05). No patient with the titers of 1 : 32 or higher had symptomatic reinfection. Serum NT antibodies to RSV of outpatients were higher than those of inpatients at reinfection.
Conclusions: The severity of illness in RSV reinfection is generally milder than that in primary infection. Our findings suggest that NT antibodies play an important role in reducing the severity of illness as well as in protection from RSV reinfection.