It's a serious setback for the Franco-Austrian laboratory Valneva. After being paused in May and then reauthorized in the United States on August 6, its chikungunya vaccine, Ixchiq, was once again suspended on August 22 by the United States Food and Drug Administration (FDA), the agency responsible for regulating medicines.

The reason: four new cases of serious adverse effects observed among vaccinated individuals in the United States, leading the agency to conclude that "this vaccine is not safe," bringing the total to over 20 cases worldwide, mainly in France and the United States. The details have not been made public or communicated to pharmacovigilance professionals.

This is the latest development in a turbulent summer saga surrounding this vaccine, the first to be approved against chikungunya – a tropical disease transmitted by Aedes mosquitoes – that caused a severe outbreak on the island of La Réunion from January to June. In its statement published on August 25, Valneva argued that the latest cases reported by the FDA brought nothing new to light and that the laboratory "is not modifying its revenue guidance at this time."

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