In a significant breakthrough, a vaccine candidate that could help prevent chikungunya has shown a 99 per cent immune response in a human clinical trial, according to a study published in the medical journal Lancet on Monday (12 June).

The phase 3 randomised controlled trial revealed the effectiveness of the VLA1553 vaccine candidate against chikungunya, with production of an immune response in 99 per cent (263/266) of participants.

The study, which was published in the peer-reviewed medical journal Lancet, also reported the vaccine candidate as generally well tolerated. Chikungunya is a viral disease that is transmitted through mosquito bites and is endemic to certain regions of Africa, Asia, and the Americas.

The symptoms of this disease include fever, headache, fatigue, nausea, and severe muscular and joint pain. The joint pain due to the disease can last for weeks, months, or even years.

Dr Martina Schneider, clinical strategy manager at Valneva, a French biotech company, highlighted the significance of this vaccine candidate, stating that it could potentially be the first chikungunya vaccine available for those living in endemic regions.

She also mentioned that it could be beneficial for travellers visiting these areas or for areas at risk for an upcoming outbreak.

"Our promising results showed good persistence of antibody levels after vaccination, which is important considering that chikungunya outbreaks may recur suddenly,” Dr Schneider said.

“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.

Chikungunya continues to afflict millions of people in India and other parts of the world every year. Currently, there are no vaccines or effective antiviral treatments available to manage the disease.

Although the researchers were unable to investigate whether the vaccine protects against subsequent disease because the study was not conducted in regions where chikungunya is endemic, they were able to test for an immune response at levels that are believed to protect against the disease in the event of infection with the virus.

“At present, there is no dedicated treatment or vaccine available against chikungunya, which is a debilitating disease whose symptoms can persist on a long-term basis,” said co-author Katrin Dubischar, programme director, chikungunya vaccine at Valneva, reports Hindustan Times.

“Moreover, it is currently regarded as one of the viruses most likely to spread globally, and studies have shown that climate change is driving the spread of the mosquitoes that carry it into new areas of the world. Therefore, having an effective vaccine is important for preparedness for future outbreaks," Dubischar added.

Furthermore, climate change is driving the spread of the mosquitoes that carry chikungunya into new areas of the world, making the need for an effective vaccine even more pressing. This will be crucial in ensuring readiness to manage future outbreaks.

The study was conducted on 4,115 healthy adults across 43 sites in the United States. Of these adults, 3,082 received one dose of VLA1553 via an arm injection, while 1,033 were given a placebo.

All participants were included in the safety analysis, while the immune response was only tested in a subgroup of 362 individuals. Within this subgroup, 266 received the vaccine, and 96 were given the placebo.

Participants were evaluated for their immune response one week, 28 days, three months, and six months after getting vaccinated.

They were also asked to record any adverse events in an electronic diary for 11 days following their vaccination.

Individuals who experienced any adverse events within 21 days after receiving the vaccine, such as neurological symptoms, fever or joint pain, heart problems, rash, or swelling were closely monitored.

After just a single vaccination, VLA1553 was found to have induced antibodies at levels effective enough to protect against the disease in 99 per cent of the participants (263/266), according to the study results. The immune response did not show any age-related variations.

The study said that VLA1553 was generally well tolerated across all age groups, with most adverse events being mild or moderate.

Headaches were the most common adverse event experienced by vaccinated individuals, occurring in 32 per cent of participants.

Fatigue (29 per cent), muscle pain (24 per cent), joint pain (18 per cent), and pain at the injection site (13 per cent) were also commonly reported side effects.

After six months, there were more adverse events recorded for those given VLA1553 than those given the placebo.

Overall, 51 per cent (1,575/3,082) of participants who were given VLA1553 and 31 per cent (322/1,033) of those who received the placebo experienced at least one adverse event that was considered related to the vaccination.

The safety profile in older adults was similar to that of other adults.

Serious adverse events were reported in 2 per cent (46/3,082) of participants exposed to VLA1553 and 1 per cent of participants in the placebo arm (8/1,033).

Two of these were classified as related to the vaccine.

One was a case of mild muscular pain in a woman with a medical history of fibromyalgia, and the other was a fever, which resulted in hospitalisation. Neither of these cases resulted in death, HT reported.

“An independent Data Safety Monitoring Board (DSMB) evaluated safety data during the study and did not identify any safety concerns after evaluating all reported adverse events,” said Juan Carlos Jaramillo, chief medical officer at Valneva.

“The two related serious adverse events reported during the study both recovered fully and were reviewed by the DSMB who did not raise concerns or consider that there were serious risks caused by the vaccination in general," Juan added.

In the study conducted for six months, VLA1553 was found to have a higher number of adverse events than the placebo.

Out of the total participants, 51 per cent (1,575/3,082) who received VLA1553 experienced at least one adverse event, while only 31% (322/1,033) of those who received the placebo reported such incidents.

The safety profile showed no significant difference for older adults compared to other adults.

Phase 3 randomized controlled trial

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