Chikungunya vaccine administered to a patient.” title=”Chikungunya the first vaccine already overtaken by serious side effects My Health”/>
At the end of 2023, American and then European health authorities authorized the first vaccine against chikungunya, a viral disease transmitted by mosquitoes, responsible for high fevers and sometimes disabling joint pain for months or even years.
Called Ixchiq, this vaccine developed by Valneva is based on so-called “live attenuated” technology. The virus is weakened to stimulate the immune system without causing illness. An effective approach, but which requires particular vigilance in certain populations.
A few months after its deployment, the first pharmacovigilance signals (monitoring system for adverse drug reactions) began to come back.
Chikungunya vaccine: serious adverse effects identified
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According to the ANSM, 47 adverse reactions were reported after administration of the Ixchiq vaccine, including 18 considered serious.
These serious effects correspond to situations requiring hospitalization, endangering life or causing significant after-effects. Among the reported cases:
In some cases, patients developed symptoms reminiscent of the disease itself, with high fever and marked joint pain. A known phenomenon with live attenuated vaccines, but generally rare.
Even more worrying, several deaths have been reported. However, as the ANSM points out, the causal link with the vaccine is not systematically established. Only one case is considered “very likely linked” to vaccination at this stage.
Well-identified risk profiles
According to ANSM data, serious cases mainly concern elderly people, with an average age around 74 years, often suffering from chronic pathologies (cardiac, metabolic or immune).
This observation is not trivial. Live attenuated vaccines are generally not recommended in immunocompromised or fragile people because their immune systems may overreact or inappropriately.
Faced with these signals, health authorities quickly adjusted their recommendations.
Reinforced precautionary measures
As soon as the first cases appeared, several decisions were taken to limit the risks. In France, as in other European countries, the use of the Ixchiq vaccine has been temporarily restricted in people aged 65 and over, while the available data is analyzed.
The European Medicines Agency (EMA) and the ANSM have also called for strengthening surveillance and an in-depth analysis of reported cases.
The objective is obviously to better understand the mechanisms at play and precisely identify risk situations.
Pharmacovigilance: how are these signals detected?
Unlike clinical trials, which involve a few thousand participants, the marketing of a vaccine exposes much larger and more diverse populations. This is when rare side effects may appear.
In France, any healthcare professional, and even patients, can report an adverse effect. These data are then analyzed by the regional pharmacovigilance centers and the ANSM.
A “signal” is triggered when several similar cases are observed. This does not automatically mean that the vaccine is the cause, but that the link must be investigated.
A vaccine under surveillance but not called into question
Side effects of the vaccine: should we be worried?
At this stage, authorities are calling for caution, but not abandonment. Because chikungunya remains a potentially serious disease, especially among the elderly. According to Public Health France, severe forms can lead to neurological, cardiac or hepatic complications, and disabling chronic pain.
In areas where the virus is actively circulating, particularly in certain tropical regions, the vaccine remains of interest. The logic therefore remains that of the benefit/risk ratio:
- in a young, healthy person exposed to the virus, the benefit of the vaccine may outweigh the risk
- in an elderly or fragile person, the scale may be different
An efficient technology… but demanding
The choice of a live attenuated vaccine partly explains the effects observed. This type of vaccine is known to induce a strong and long-lasting immune response, often with just one injection. But it can also, in rare cases, cause symptoms similar to the disease.
This is why it is already used cautiously for other infections, such as yellow fever. These vaccines are generally contraindicated in immunocompromised people and not recommended in frail elderly people.
NAMELY
Chikungunya is transmitted through the bite of infected mosquitoes, mainly the tiger mosquito. In France, this mosquito is now established in a large part of the territory, which explains the increased surveillance around this disease, according to Public Health France.
