Chikungunya: Ixchiq vaccine suspended in the United States after new adverse effects

U.S. health authorities have suspended the approval of Ixchiq, a chikungunya vaccine developed by the Franco-Austrian laboratory Valneva, basing their decision on new reports of side effects, the company announced. "This suspension is effective immediately and involves a suspension of the shipment and sale of Ixchiq in the United States," Valneva detailed in a press release dated Monday, August 25.

This vaccine is one of the first to be developed against chikungunya, a viral disease transmitted from one human to another by mosquito bites. French health authorities had made it a central tool in the fight against a major epidemic in Réunion in the spring. But its deployment was disrupted by the reports of around twenty serious effects, all in elderly people. According to the latest report, one death on site is very likely linked to the vaccine.

In this context, the vaccine had been suspended for those over 65 by France, then by the European Union (EU). But the latter reauthorized it in July, judging that its side effects did not call into question its value in combating a disease that is particularly high-risk among the elderly. In the meantime, the suspension of the vaccine had, in effect, reduced vaccination in Réunion to almost zero.

The United States, through its Food and Drug Administration (FDA), has decided to suspend the vaccine for everyone, explaining this decision by the reports of new serious side effects in the country: four in patients aged between 55 and 82.

This choice "is based on serious concerns about the safety of the vaccine, which appears to cause disorders similar to chikungunya," the FDA states on its website, assuring that "the benefits of the vaccine do not compensate for its risks, according to the most plausible scenarios . " "This vaccine is not safe," and its continuation "would pose a health hazard," it insists.

The decision comes as many researchers are concerned that US health policy is taking a vaccine-sceptic turn under President Trump's appointment to head the Department of Health and Human Services. In the latest move, the United States will stop funding the development of several mRNA vaccines, a technology that has led to the creation of the most effective Covid-19 vaccines.

Without directly criticizing the FDA's decision, Valneva described the suspension as "sudden" and considered the newly reported side effects "comparable" to those already known. The group has not yet revised its financial forecasts accordingly, but says it is assessing the financial impact that a permanent withdrawal of the vaccine in the United States could have. At the opening of the Paris Stock Exchange on Monday, the laboratory's shares fell 26.46% to 3.71 euros.