Chikungunya Vaccine Confirmed Effective and Safe

Since 2014, the Federative Republic of Brazil has been confronting chikungunya virus outbreaks without being able to offer its massive population access to an effective and safe vaccine.

During 2024, Brazil's situation has intensified. 

As of September 2024, over 383,000 chikungunya cases and 165 related fatalities have been reported this year.

The vaccine access shortcoming has recently been eliminated with the approval of Valneva SE's IXCHIQ® (VLA1553) monovalent, single-dose, live-attenuated vaccine.

In late 2023, IXCHIQ became the first vaccine approved by the U.S. FDA to address chikungunya virus (CHIKV) infections in adults at increased risk of exposure to the mosquito-transmitted disease.

In Brazil, public health leaders believe adolescents and teenagers are a sensitive population who would benefit from a prophylactic vaccine.

A recent phase 3 clinical trial assessed the immunogenicity and safety of the IXCHIQ vaccine to understand better the benefits of a broad vaccination program that includes younger people.

On September 4, 2024, researchers reported in The Lancet Infectious Disease data on safety and immunogenicity 28 days after vaccination.

Between February 2022 and March 2023, 754 participants received a trial vaccination (502 received VLA1553 and 252 received placebo) with a per-protocol population of 351 participants for immunogenicity analyses (303 in the VLA1553 group and 48 in the placebo group).

In seronegative participants at baseline, VLA1553 induced seroprotective chikungunya virus neutralizing antibody levels in 247 of 250 (98·8%, 95% CI 96·5–99·8) participants 28 days after vaccination.

In seropositive participants, the baseline seroprotection rate of 96.2% increased to 100% after vaccination with VLA1553.

Most (93%) adverse events were of mild or moderate intensity, and VLA1553 was generally well tolerated.

After administration of VLA1553, there was a significantly lower frequency of solicited adverse events in participants who were seropositive at baseline compared with those who were seronegative (53% vs. 74%; p<0·0001), including headache, fatigue, fever, and arthralgia.

In an accompanying Editorial, researchers wrote, 'VLA1553 was generally safe and induced seroprotective titers in almost all vaccinated adolescents with favorable safety data in adolescents who were seropositive at baseline.'

Furthermore, 'the data support using VLA1553 to prevent disease caused by the chikungunya virus among adolescents and in endemic areas', such as Brazil.

So far this year, 79 travel-related chikungunya cases have been detected in the U.S., on pace to exceed the 94 cases reported in 2023.

As of September 10, 2024, IXCHIQ was available for adults in the Americas, Canada, and Europe. Most travel clinics and pharmacies in the U.S. offer IXCHIQ vaccination services.

The Coalition funded this study for Epidemic Preparedness Innovation and EU Horizon 2020. No industry conflicts of interest were disclosed.