Kinetics of IgG-specific antibodies against chikungunya virus in a female cohort study in Brazil, 2018-2019

The kinetics of IgG-specific antibody responses against chikungunya virus (CHIKV) is poorly understood. A total of 559 paired serum samples were collected at baseline and at first follow-up in a cohort of women aged 15-39 years from endemic areas of Fortaleza, Ceará State, following the major 2017 outbreak from February 2018 to August 2019. To estimate longitudinal seroprevalence, combining antibody markers (anti-CHIKV IgM and IgG) were screened by using enzyme-linked immunosorbent assays. We found an overall seroprevalence of 34% (190/559; 95%CI, 30.2-38.0) and 31.3% (175/559; 95%CI, 27.6-35.3) at baseline and first follow-up, respectively. Also, the distribution of seroprevalence did not differ significantly by age group [15-24 years, 35.4% (92/260); 25-39 years, 32.8% (98/299)]. Additionally, we found that median IgG level decreased over time across all age groups, and independent of prior history of symptomatic infection. We also observed four cases of seroreversion. Our findings provided valuable information regarding the decline of anti-CHIKV IgG levels in a post-epidemic scenario, highlighting the importance of serological surveillance to better understand the kinetics of antibody responses and to characterize epidemic risk.