Chikungunya Re-emergence Prompts French Health Authority to Define Vaccine Strategy for French Guiana

The High Authority of Health (HAS) has released crucial guidance on the use of two chikungunya vaccines, IXCHIQ and VIMKUNYA, in French Guiana, following a significant re-emergence of the virus in the territory. The directive, issued in February 2026 at the request of the Directorate General of Health (DGS), aims to clarify the roles of these vaccines in the evolving public health landscape of the region, where cases have been on the rise since January 2026.

The HAS’s comprehensive assessment took into account a range of critical factors, including the most recent epidemiological data from French Guiana, the specific characteristics of the available vaccines, and the existing public health infrastructure. This proactive approach underscores the French health authorities’ commitment to managing and mitigating the impact of infectious diseases in its overseas territories, which often face unique epidemiological challenges.

Epidemiological Landscape: A Resurgent Threat

Santé publique France, the national public health agency, has sounded the alarm regarding the resurgence of chikungunya cases in French Guiana. Since January 2026, the virus has demonstrated a notable circulation, with the majority of detected outbreaks concentrated in the western coastal region. As of April 9, 2026, a total of 81 cases have been biologically confirmed through RT-PCR testing, indicating the presence of the viral genome. Notably, 10 of these confirmed cases were reported during the week of March 25-31, 2026, signaling a concerning acceleration in transmission.

The HAS’s assessment highlighted that a decade has passed since the last major chikungunya epidemic in French Guiana. This prolonged period without widespread transmission has led to a seroprevalence rate within the population that is insufficient to confer collective immunity. This lack of widespread immunity among the general population makes them more vulnerable to infection and potential severe outcomes, thus necessitating a strategic vaccination approach. The emergence of these new cases underscores the cyclical nature of arboviral diseases and the importance of continuous surveillance and preparedness.

Chikungunya, a mosquito-borne viral illness, is characterized by abrupt onset of fever, severe joint pain, muscle pain, headache, nausea, fatigue, and rash. While most individuals recover within a week or two, some can develop chronic joint pain that can persist for months or even years, significantly impacting quality of life. In certain demographics, particularly the elderly and those with underlying health conditions, chikungunya can lead to more severe complications, including neurological disorders and cardiac issues, underscoring the public health imperative to control its spread.

VIMKUNYA: Targeted Protection for Vulnerable Populations

In response to the heightened epidemic risk and the urgent need to shield individuals most susceptible to severe chikungunya, the HAS has recommended the use of VIMKUNYA, a protein subunit vaccine with adjuvant, for specific demographic groups in French Guiana. This recommendation is rooted in the vaccine’s established safety profile and its ability to elicit a robust immune response.

VIMKUNYA is specifically recommended for:

• Individuals aged 65 and older, regardless of their comorbidity status: This age group is known to be at a higher risk of developing severe chikungunya and its complications.
• Individuals aged 12 to 64 with comorbidities: This includes individuals with pre-existing health conditions such as diabetes, cardiovascular disease, chronic respiratory diseases, kidney disease, or compromised immune systems, which can exacerbate the severity of chikungunya infection.

The HAS acknowledges that VIMKUNYA can also be considered for other populations, provided that several caveats are carefully observed. These include the documented limited duration of protection, which has been shown to last for approximately six months. Furthermore, the absence of data specifically pertaining to its use in immunocompromised or immunodeficient individuals necessitates a cautious approach. For these populations, a thorough risk-benefit analysis on an individual basis is paramount before administration.

A critical point of consideration for VIMKUNYA is its use in pregnant and breastfeeding women. The HAS explicitly states that the vaccine is not recommended for these groups due to a lack of specific tolerance data. However, the authority nuances this by stating that VIMKUNYA does not present a contraindication in principle, given its protein-based composition with an adjuvant. Therefore, it could potentially be offered on a case-by-case basis. Such a decision would require an in-depth evaluation of the individual risk of exposure to chikungunya, coupled with a comprehensive assessment of the potential benefits and risks for the pregnant woman, the fetus, and the newborn. This nuanced approach reflects the complexity of public health decisions involving vulnerable populations and the need for individualized medical judgment.

IXCHIQ: A Live-Attenuated Option with Specific Restrictions

The HAS’s recommendations for IXCHIQ, a live-attenuated vaccine, align with its previously established guidelines, which are now being applied to the French Guianese context. These recommendations are designed to leverage the vaccine’s efficacy while mitigating potential risks associated with its live-attenuated nature.

For individuals aged 18 to 64 years without comorbidities, IXCHIQ can be offered. However, this recommendation comes with important stipulations. An in-depth assessment of potential benefits and risks is required. Crucially, the HAS notes the existing data gaps regarding the safety of IXCHIQ in individuals aged 12 to 17 years who present with clinical conditions associated with altered or deregulated immune responses. This lack of comprehensive data necessitates a cautious approach for younger individuals with compromised immune systems.

A significant restriction remains for individuals aged 65 and older. The HAS is maintaining its previous suspension of IXCHIQ’s use in this age group. This decision stems from pharmacovigilance signals that emerged from previous safety monitoring, as detailed in a HAS opinion dated April 25, 2025. While specific details of these signals were not elaborated upon in this particular update, the sustained caution indicates a continued concern regarding the vaccine’s safety profile in older adults.

As a live-attenuated vaccine, IXCHIQ carries inherent characteristics that dictate its usage. It is contraindicated in pregnant women due to the potential risk to the fetus. Similarly, it is not recommended for immunocompromised or immunodeficient individuals, as their weakened immune systems may not effectively control the attenuated virus, potentially leading to uncontrolled replication and disease. The HAS also reiterates its prior stance, issued on July 17, 2025, that there is no evidence to support a specific recommendation for the use of IXCHIQ in individuals suffering from sickle cell disease. This indicates that while not explicitly contraindicated, there is no compelling clinical rationale for prioritizing IXCHIQ for this patient group.

Consolidated Vaccination Strategy for French Guiana

To provide a clear and actionable framework for healthcare professionals in French Guiana, the HAS has summarized its recommendations in a table. For both IXCHIQ and VIMKUNYA, the recommended vaccination schedule consists of a single dose.

Table: HAS Vaccination Recommendations for Chikungunya in French Guiana (April 14, 2026)

| Population Group | Vaccine Recommendations