Valneva shares rose on Tuesday after the specialty vaccine maker reported that a single dose of its Ixchiq chikungunya vaccine maintained antibodies for five years.
The biotechnology company announced on Tuesday, November 10, that 94% of participants in its clinical follow-up study retained a seroresponse five years after receiving one injection of Ixchiq. At the four-year mark, the antibody persistence rate stood at 95% among the 221 adults still tracked in the trial.
On the Paris stock market, Valneva shares gained 2.6% around 14:45 local time on Tuesday, according to financial news outlet BFM Bourse. That advance followed a 3.44% gain on Monday as the company delivered a series of positive clinical updates.
Five-year Ixchiq antibody persistence data
According to Valneva, the five-year persistence of antibodies was comparable between older adults aged 65 and over and younger adults aged 18 to 64. The company added that the long-term follow-up study will continue for a total of 10 years to monitor ongoing immune durability.
In a press release, Valneva said the latest findings confirm durable antibody persistence across all vaccinated age groups and corroborate earlier data published from the programme. The company stated that the results met its expectations, reinforcing the differentiated profile of Ixchiq and its ability to offer long-term protection from a single dose in the same way as other live-attenuated vaccines.
A seroresponse measures whether a vaccinated person maintains protective antibodies in the blood above a set threshold. Live-attenuated vaccines use a weakened version of a virus to trigger a broad and lasting immune response, often avoiding the need for the multiple doses or regular booster shots required by inactivated vaccines.
Global approvals and safety restrictions for Ixchiq
Ixchiq is currently marketed in the European Union, in Canada, and, since April 2025, in Brazil. Regulatory authorisation in Brazil marked a major milestone for the programme because it was the first approval of the vaccine in a country where chikungunya is endemic.
Chikungunya is a mosquito-borne viral disease transmitted to humans by infected Aedes mosquitoes. The illness causes acute fever and severe joint pain that can become chronic and debilitating, alongside muscle aches, headaches, and fatigue, primarily affecting tropical and subtropical regions.
Analysts at research firm Allinvest Securities noted that the five-year data strengthens the main clinical advantage of Ixchiq, which is the ability to provide lasting protection after a single injection. According to the firm, single-dose immunity is particularly valuable when responding to unpredictable epidemic outbreaks.
However, Allinvest Securities tempered the impact of Tuesday's announcement. The research firm pointed out that the five-year figures are largely confirmatory and do not directly resolve the safety and tolerability concerns that led to the withdrawal of the vaccine in the United States and the restriction of its use in Europe to individuals at high risk of infection.
According to Allinvest Securities, the primary challenge for Valneva now is to gather real-world effectiveness and safety data. The analysts highlighted the ongoing monitoring of approximately 80,000 adults vaccinated in Brazil, noting that favourable data from that cohort could help restore confidence among regulatory authorities and support broader commercial uptake of Ixchiq.
Shigellosis vaccine results and market potential
Tuesday's stock gain built on momentum from Monday, November 9, when Valneva released encouraging interim clinical results for its vaccine candidate targeting shigellosis. There is currently no approved vaccine anywhere in the world for the acute infectious diarrhoeal disease.
Shigellosis is an intestinal infection caused by Shigella bacteria, typically spread through contaminated water or food. According to figures cited in the report, it is the second leading cause of diarrhoeal mortality worldwide and places a heavy burden on young children, causing up to 165 million infections each year, including 62.3 million cases among children under the age of five.
Valneva stated that developing a vaccine against the potentially fatal infection represents a major public health priority across many regions of the world. Allinvest Securities estimated that the potential annual market for a shigellosis vaccine exceeds $500 million, though the firm cautioned that advancing the programme through further development will require substantial clinical investment.
Lyme disease vaccine candidate VLA15
Headquartered in Saint-Herblain, France, Valneva specialises in developing and commercialising vaccines for infectious diseases with significant unmet medical needs. Beyond Ixchiq and its shigellosis candidate, the company's next major catalyst involves VLA15, its experimental vaccine against Lyme disease.
Lyme disease is a tick-borne bacterial infection caused by Borrelia bacteria that can lead to severe joint, heart, and nervous system complications if untreated. Valneva is awaiting regulatory approval to commercialise VLA15 in the United States, and Allinvest Securities previously identified the Lyme disease shot as the company's primary valuation driver.
