Persistent neutralizing antibodies against chikungunya virus eight years after infection

Chikungunya fever, caused by the mosquito-borne chikungunya virus (CHIKV), poses a significant global health burden, with an estimated 16.9 million infections annually. Although CHIKV infection induces neutralizing antibody responses, data on their long-term persistence remain limited. In July 2017, an imported outbreak caused by the CHIKV East/Central/South African genotype occurred in Zhejiang Province, China. To assess the longevity of neutralizing antibodies, we conducted a cross-sectional follow-up study in August 2025, approximately eight years after infection. Two laboratory-confirmed patients from the outbreak were enrolled, and serum samples were collected. Serum neutralizing antibodies were measured using both pseudovirus and authentic CHIKV neutralization assays. Remarkably robust and sustained responses were observed in both patients. The pseudovirus neutralization titers were 225,677 and 134,460, respectively, and authentic virus neutralization titers were 9,133 and 4,951, respectively—which substantially exceeded the established protective threshold of 150. As no subsequent CHIKV outbreaks were documented in this non-endemic region, these high neutralizing antibody titers indicate that durable immunity may be derived from a single infection rather than repeated boosting. These findings suggest that natural CHIKV infection can elicit neutralizing antibodies that persist at high levels for at least eight years, providing evidence to inform the development of vaccines and vaccination strategies.