Twelve months after a single shot of Valneva SE’s chikungunya vaccine, positive antibody persistence was found, threatening a deadly disease that has long resisted treatment. The new data are derived from a study of 363 healthy adult participants that followed them from month 6 after vaccination to month 12. Nearly all, 99%, kept their neutralizing antibody titers for 12 months beyond the seroresponse threshold of 150, which hit the primary endpoint and the antibody level agreed with regulators as endpoint under the accelerated approval pathway.