When a new disease struck the people of southern Tanzania in 1952, they named it after the most striking symptom: the suffering that bends people. In their language: Chikungunya. The disease, which is now known to be caused by a virus and transmitted by mosquitoes, can cause fever, skin rashes and flu-like symptoms and joint pain that is so severe that people are writhing in their suffering. In about a third of those infected, the torment lasts for weeks. For some months or even years.
Chikungunya fever has now appeared in more than 100 countries, mainly in Africa, Asia and South America. there are still no targeted drugs or vaccines. But researchers are now working on several vaccines. The first, a product from the French company Valneva, has now completed the third and final phase of the study. Applications for approval have already been submitted in the USA and Europe.
The results of these tests initially look good. Almost all study participants had developed an immune response against the virus 28 days after receiving a dose of vaccine. The company’s researchers wrote that 99 percent of the 263 adult subjects had formed sufficiently high levels of neutralizing antibodies in the journal lancet. Even half a year after the vaccination, the antibodies remained at a high level. The nearly 100 people in the control group showed no corresponding immune response.
It is unclear to what extent vaccinations actually prevent infections or diseases
The study was conducted in the United States, where Chikungunya infections are sporadic. And that is the biggest weakness: It was not possible to determine to what extent vaccinations actually prevent infections or diseases in the country that is hardly affected. Only antibody titers were measured.
The US regulatory authority FDA and its European counterpart, the EMA, had approved this procedure, “Because conventional efficacy studies are impractical in real-world outbreaks of chikungunya (which are unpredictable and fast-spreading),” writes Kathryn Stephenson of Harvard Medical School in an accompanying comment in the lancet.
The vaccine, called VLA1553, is believed to offer some protection against the disease. “We know from earlier studies of this type that high neutralizing antibody concentrations in viral infections also correlate with prevention of the disease,” says Peter Kremsner, director of the Institute for Tropical Medicine at the University Hospital in Tübingen.
The product is also a live vaccine; such vaccines are usually very effective. A weakened pathogen is administered to the body, which no longer causes illness and only multiplies to a very limited extent, but which boosts the immune system. But who he protects in the end, how much and for how long remains open in the current case.
Another weakness of this approach is that it’s not clear how well the results translate to those people who need protection most: residents of known endemic areas, whose health, immune systems, and living conditions may be very different from those in the previous test area. “Ultimately, strictly speaking, it’s ‘just’ a travel vaccination,” says Kremsner.
The disease is conquering more and more areas
The tolerability of the vaccine was also only checked in the USA, but with more volunteers than in the efficacy tests. About 4,100 people received the vaccine, almost 3,100 a dummy preparation. Serious symptoms occurred in 1.5 percent of those vaccinated and 0.8 percent in the placebo group. Overall, the authors described the product as “generally well tolerated”.
Thirteen women who received the vaccine became pregnant during the study period. Three of them gave birth to their child prematurely. This proportion is slightly higher than one would expect, although two of the women were already at risk of preterm birth. The number of three events is ultimately too small to be able to evaluate them statistically with certainty.
According to the World Health Organization (WHO), more than two million people have contracted chikungunya fever since 2005 alone. The areas where transmission occurs are expanding – a development that climate change is likely to fuel. Europe could also see more diseases in the future.
The first transmissions were observed on the continent as early as 2007; at that time there was an outbreak with more than 200 infected people in Italy. In the following years, cases were also reported from France. The risk of the virus spreading in the EU in the future is high, writes the European disease control agency ECDC. She points out that the vector mosquitoes of the type aedes widespread in many countries of the Community, but particularly on the Mediterranean coast.
Also in parts of Germany Aedes albopictus, also known as the Asian tiger mosquito, has already been sighted. Researchers at the Robert Koch Institute recently warned that global warming is increasing the likelihood that what was once tropical fever will also be transmitted here in the future.
With material from the Science Media Center