A new single-dose chikungunya vaccine, developed by French biotech Valneva is safe and produces an immune response, according to a phase 3 randomised controlled trial published in The Lancet.

After a single vaccination, VLA1553 induced antibody levels at a level that is considered to protect against disease among 99 per cent (263/266) of participants. There was no difference in immune response according to age.

While antibody levels declined 28 days after vaccination, seroprotection persisted in more than 96 per cent (233/242) of participants after six months.

"This could be the first chikungunya vaccine available for people living in endemic regions, as well as for travellers to endemic areas or areas at risk for an upcoming outbreak," said lead author Martina Schneider, Clinical Strategy Manager at Valneva.

"Our promising results showed good persistence of antibody levels after vaccination, which is important considering that chikungunya outbreaks may recur suddenly. As age is a risk factor for severity and mortality of chikungunya disease, the strong immune response observed in older participants might be particularly beneficial," Schneider added.

However, the trial on VLA1553-301 was conducted in the US, not in regions where chikungunya is endemic. As a result, researchers were unable to investigate whether the vaccine protects against subsequent disease.

Instead, the study tested for an immune response at levels that are thought to protect against the disease if infected with the virus.

Chikungunya is a mosquito-borne disease caused by the chikungunya virus (CHIKV), which is endemic in some regions of Africa, Asia, and the Americas. It causes a fever in patients roughly four to eight days after they have been bitten by an infected mosquito. Symptoms include headaches, fatigue, nausea, and severe muscle and joint pain.

Currently, there are no approved vaccines to prevent the disease caused by CHIKV infection nor are there effective antiviral treatments for the disease.

The study enrolled 4,115 healthy adults across the US. Of these 3,082 participants were given one dose of VLA1553 (via an injection in the arm), and 1,033 were given a placebo.

VLA1553 was generally well tolerated across all age groups with most adverse events being mild or moderate. In those given the vaccine, the most common adverse events were headaches (experienced in 32 per cent of vaccinated participants), fatigue (29 per cent), muscle pain (24 per cent), joint pain (18 per cent), and pain at the injection site (13 per cent).

After six months, 51 per cent of participants who were given VLA1553 and 31 per cent of those who received the placebo experienced at least one adverse event that was considered related to the vaccination.

The rate of observed miscarriages in the population given VLA1553 was slightly higher than expected in the general population (23 per cent versus around 11-16 per cent). However, this could be due to natural variation in the small sample size, the researchers said.

The researchers acknowledged some limitations such as the vaccine being made from a weakened version of the live virus, so is likely to be unsuitable for people with weakened immune systems and pregnant women.