Antibody Responses to Respiratory Syncytial Virus: A Population-Based Cross-Sectional Serological Study in Southern China, 2021

Objectives With remarkable progress in the field of RSV prophylaxis, it is critical to understand population immunity against RSV. We aim to describe the RSV pre-F immunoglobin G (IgG) antibodies across all age groups in southern China and evaluate the risk factors associated with lower antibody levels. Methods We conducted a community-based cross-sectional sero-epidemiological study in Anhua County, Hunan Province, southern China, from July to November 2021. Serum samples were tested for IgG antibodies against the RSV prefusion F (pre-F) protein using an enzyme-linked immunosorbent assay. We estimated the geometric mean titres (GMTs) and seropositivity rates across all age groups. Generalized linear models (GLMs) were built to identify factors associated with antibody levels. Results A total of 890 participants aged 4 months to >89 years were enrolled. The lowest RSV pre-F IgG GMTs were observed in infants and toddlers aged 4 months to <2 years (3.0, 95% confidence interval [CI]: 2.6-3.5). With increasing age, RSV pre-F IgG GMT increased to 4.3 (95% CI: 4.1-4.4) between the ages of 2 and <5 years and then stabilized at high levels throughout life. All the children had serological evidence of RSV infection by the age of 5 years. Age was associated with RSV pre-F antibody levels in children, with an estimated 1.8-fold (95% CI: 1.1-2.9) increase in titre per year before 5 years of age, while it was not significantly associated with antibody levels in adults aged >60 years. Conclusions Our findings could provide a comprehensive understanding of the gaps in RSV immunity at the population level and inform the prioritization of immunization platforms.