Chikungunya is a mosquito-borne disease caused by the chikungunya virus (CHIKV), which is endemic in parts of Africa, Asia and the Americas. It causes fever in patients about four to eight days after being bitten by an infected mosquito. Symptoms include headaches, fatigue, nausea, and severe muscle and joint pain.
Joint pain is often debilitating and usually lasts a few days, but can be prolonged and last for weeks, months or even years. Serious illness and death are rare, but the elderly and newborns are most at risk. There are currently no approved vaccines to prevent disease caused by CHIKV infection, nor are there effective antiviral treatments for the disease.
The study’s lead author, Dr. Martina Schneider, clinical strategy manager at Valneva, says: “This could be the first chikungunya vaccine available for people living in endemic areas, as well as for travelers to endemic areas or areas at risk of an upcoming outbreak.
Our promising results showed good persistence of antibody levels after vaccination, which is important given that chikungunya outbreaks can suddenly recur. Since age is a risk factor for the severity and mortality of chikungunya disease, the strong immune response observed in older participants could be particularly beneficial.
Study author Katrin Dubischar, Program Director, Chikungunya Vaccine in Valneva, says: “There is currently no specialized treatment or vaccine available for chikungunya, a debilitating disease whose symptoms can persist for a long time.
The study enrolled 4,115 healthy adults at 43 study sites in the United States. 3,082 participants were given a single dose of VLA1553 (by injection in the arm) and 1,033 were given a placebo. All participants were included in the safety analysis, but the immune response was only tested in a subset of 362 participants (266 received vaccine and 96 placebo).
Participants had their immune response assessed one week, 28 days, three months and six months after vaccination. They also recorded adverse effects in an electronic diary for 11 days after vaccination. Those who experienced adverse events within 21 days of vaccination (eg, fever and joint pain, back pain, neurological symptoms, heart problems, rash or swelling) were followed more closely.
After a single vaccination, VLA1553 induced antibody levels at a level considered protective against disease in 99% (263/266) of participants. There was no difference in immune response by age.
VLA1553 was generally well tolerated in all age groups, with most adverse events being mild or moderate in severity. In those who received the vaccine, the most common side effects were headache (reported in 32% of vaccinated participants), fatigue (29%), muscle pain (24%), joint pain (18%), and pain at the injection site ( 13 %).
After six months, more adverse events were reported in patients receiving VLA1553 than in patients receiving placebo. Overall, 51% (1,575/3,082) of participants who received VLA1553 and 31% (322/1,033) of those who received placebo experienced at least one adverse event that was considered related to vaccination. The safety profile in older adults was similar to that in adults.
The frequency of observed abortions in the population receiving VLA1553 was slightly higher than expected in the general population (23% versus approximately 11-16%). However, this could be due to natural variation in the small sample size. Two of the three miscarriages in women given VLA1553 were explained by a genetic disorder or the participants’ history of miscarriage.
Commenting on the safety results of the study, Dr Juan Carlos Jaramillo, chief medical officer at Valneva, says: “The independent Data Safety Monitoring Board (DSMB) evaluated the safety data during the study and after evaluating all reported adverse events, found no safety risks. Events.
The authors point out some limitations of their study. The study was not conducted in an endemic area, so participants’ preexisting immunity to chikungunya virus is unknown, as is the safety of the vaccine in this population. In addition, the vaccine is made from a weakened version of the live virus, so it is probably unsuitable for people with weakened immune systems and pregnant women.
Dr. Kathryn Stephenson of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center, who was not involved in the study, said in an attached comment: “…the positive results of this study are very good news for CHIKV pandemic preparedness., will be essential to confirm the value of VLA1553 for CHIKV prevention, as well as real-world efficacy studies in the context of actual CHIKV outbreaks. .”
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