A live vaccine under development by the Franco-Austrian company Valneva against Chikungunya fever provokes a strong neutralizing antibody response in individuals. This is the result of a first phase III study in the USA, which has now been published in the journal “Lancet Infectious Diseases”. However, there is still no evidence of a protective effect “in the field”.
Chikungunya has received increasing attention in recent years. The name means “the stooped walker”, a reference to the sometimes severe joint problems associated with an illness. Infection occurs mainly through the bite of infected mosquitoes of the genera Aedes albopictus (tiger mosquito) and Aedes aegypti (yellow fever mosquito). These mosquitoes are found in many cities and regions in the tropics and subtropics and bite mainly during the day.
Due to climate change, the distribution areas of mosquito species that transmit the infection have increased. In Italy, for example, an outbreak involving more than 300 patients first occurred in 2007, and smaller outbreaks have also been reported in southern France in recent years. All people who have been affected in Austria so far have been infected while traveling and no domestic transmission has been reported. In recent years, there have been around five million cases of Chikungunya in around 100 countries around the world.
For these reasons, biotechnology and pharmaceutical companies have tried to develop vaccines against the infection or disease in recent years. The Franco-Austrian company Valneva has a live vaccine with weakened and non-pathogenic viruses.
Because chikungunya outbreaks are unpredictable and outbreaks of the disease can disappear quickly, vaccine testing is difficult. The study conducted by Martina Schneider (Valneva/Vienna) and her co-authors was therefore not about fighting the disease in an endemic area. Instead, between September 17, 2020 and April 10, 2021, nearly 4,100 subjects were enrolled in the study at 43 study centers across the US – all in regions with no cases of Chikungunya.
In the study, about 3,100 subjects (randomly selected) received a dose of the vaccine candidate VLA1553 and just over 1,000 received a placebo. As planned, after the single vaccination, blood samples were tested for any immunological reactions in 266 subjects in the VLA1553 group and 96 subjects in the placebo group. The main result, according to the scientists in “Lancet Infectious Diseases.” “VLA1553 produced protective antibody levels in 263 (98.9 percent) of 266 subjects in the VLA1553 group 28 days after immunization.” This was true for all age groups. After 180 days, 96.3% of those vaccinated apparently still had enough protective antibodies in their blood.
The vaccine was well tolerated. Adverse reactions primarily involved headache (32 percent of those immunized), fatigue (29 percent), joint pain (18 percent), and pain at the injection site (13 percent).
More serious side effects occurred in just two percent of those actually vaccinated and one percent of placebo subjects. Only two of the cases were classified as likely vaccine-related. Martina Schneider (Valneva): “This could be the first Chikungunya vaccine for people in endemic areas, but also for travelers to regions where Chikungunya outbreaks are imminent.”
However, the results of this study are based purely on lab tests. There is still a lack of evidence of the protective effect of the Valneva candidate vaccines under the actual conditions of a Chikungunya outbreak or in endemic areas. Such a study is underway in Brazil, for example. The company wants to get approval for the vaccine in the US, EU and other countries.
But there are also potential important limitations: live vaccines are often considered unsuitable for people with compromised immune systems and for pregnant women. Internationally, other companies are also involved in Chikungunya vaccine research. Valneva should currently be at the top here. The company has had a Japanese encephalitis vaccine for years. A Covid-19 vaccine project has met with little commercial success. A vaccine against Lyme disease is also being developed jointly with the US pharmaceutical company Pfizer.
In any case, protective vaccines against Chikungunya can be of great help both for people in affected regions and for travelers. After all, about half of those infected subsequently developed severe rheumatic joint problems. The mortality rate is given as 0.3 for one case per 1000 patients.