RESUMO
OBJECTIVES: With remarkable progress in the field of respiratory syncytial virus (RSV) prophylaxis, it is critical to understand population immunity against RSV. We aim to describe the RSV pre-F IgG antibodies across all age groups in Southern China and to evaluate the risk factors associated with lower antibody levels. METHODS: We performed a community-based cross-sectional sero-epidemiological study in Anhua County, Hunan Province, Southern China, from July 15, 2021, to November 5, 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. The generalized linear models were built to identify factors associated with antibody levels. RESULTS: A total of 890 participants aged 4 months to older than 89 years were enrolled. The lowest RSV pre-F IgG GMTs were observed in infants and toddlers aged 4 months to younger than 2 years (3.0; 95% CI, 2.6-3.5). With increasing age, the RSV pre-F IgG GMT increased to 4.3 (95% CI, 4.1-4.4) between the ages of 2 and younger than 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, although it was not significantly associated with antibody levels in adults aged older than 60 years. DISCUSSION: Our findings could provide a comprehensive understanding of the gaps in RSV immunity at the population level and inform the prioritization of immunization platforms.
RESUMO
China has achieved high vaccination coverage under the Expanded Program on Immunization (EPI) in children 1-2 years of age. However, a knowledge gap exists regarding vaccination coverage and timeliness for children >2 years of age. As such, this study aimed to estimate coverage and timeliness for all EPI and selected non-EPI vaccines within a rural area of China. Immunization data for 5091 children, born between September 2003 and November 2015, were collected from vaccination cards obtained during sero-surveillance follow-up visits and/or from the Hunan immunization information system. For each dose of both EPI and non-EPI vaccines, vaccination coverage and timeliness were calculated, and temporal variations were examined across birth cohorts. We found coverage for EPI vaccines scheduled for <12 months was 97.1%-99.4%. However, for EPI vaccines scheduled at 6 years coverage was 44.4%-51.7%. The timeliness for EPI vaccines was generally poor, especially for EPI vaccines introduced after 2008 or scheduled for administration at ≥12 months, with a maximum of 35.4% of children vaccinated according to schedule. Despite this, we found increasing trends in vaccination coverage and improvements in timeliness for EPI vaccines. However, for non-EPI vaccines, we found only moderate increases, and in some cases decreases, in vaccination coverage. This study demonstrates the success and improvement of the Chinese immunization program, but also highlights some challenges to be addressed. We recommend that future changes in vaccine practice and policy should primarily focus on improving coverage and timeliness of vaccines introduced after 2008, and/or scheduled for administration ≥12 months.
