Valneva has reported encouraging six-month safety and antibody persistence data from the multi-centre Phase II trial, VLA1553-221, of its chikungunya vaccine, Ixchiq, in 304 healthy paediatric subjects between one and 11 years of age.

This randomised, observer-blinded, dose-response trial aims to support a future pivotal Phase III trial to potentially extend the vaccine's label to include this younger demographic.

Valneva anticipates commencing this trial in the first quarter of 2026.

The Phase II trial was funded in part by the Coalition for Epidemic Preparedness Innovations (CEPI), with support from the EU.

It is being conducted across three sites in Honduras and the Dominican Republic, assessing the safety and immunogenicity of two varied dose levels of the vaccine.

Subjects in the trial were randomised and given either a full dose of the licensed Ixchiq formulation and presentation, a half dose, or an active control (Nimenrix).

The six-month outcomes of the trial align with initial data reported this January, indicating that a full dose elicited a stronger immune response at day 15 and day 180 after vaccination, compared with a half dose.

The immune response profile in children was consistent with previous observations in adults and adolescents.

A notable 96.5% seroresponse rate was observed at day 180 in chikungunya virus (CHIKV)-naïve children who received the full dose.

The vaccine was tolerated well across all doses in children, without any safety concerns observed.

According to the company, the comparability of the vaccine doses in terms of tolerability and safety, along with the enhanced immune response of the complete dose for all tested age groups up to day 180 after vaccination, supports the use of the full dose in the paediatric population.

Valneva chief medical officer Juan Carlos Jaramillo said: “The six months persistence and safety data in children are aligned with the robust antibody response and safety profile we reported in adolescents after a single vaccination. Considering the significant risk chikungunya poses to individuals living in or travelling to endemic areas, it is crucial to ensure that the vaccine is accessible to people of all ages and capable of potentially offering long-term protection from a single shot.”

This development follows Valneva and Pfizer's previous announcement of positive data from the Phase II VLA15-221 trial of a second booster dose of their Lyme disease vaccine candidate, VLA15, administered one year after the initial booster.