Brazil develops the first vaccine against schistosomiasis, the disease of swollen bellies

Brazil is a few steps away from manufacturing the world’s first vaccine against schistosomiasis, a disease caused by worms that causes large swollen bellies in children and adults in the poorest regions of the southern hemisphere, especially in Africa. The discovery is the work of a team from the Oswaldo Cruz Foundation, a public body based in Rio de Janeiro.

Preclinical tests of the vaccine called Shistovac (sm14) in laboratory animals were able to reduce Schistosoma masnoni infections in mice and rabbits by more than 90%. In humans, the vaccine was shown to be safe, with the main side effect being pain in the area of application. Miriam Tendler, the researcher who has been leading the vaccine team for years, tells EL PAÍS that the results “have been excellent from phase one.”

At the moment, the researchers are finishing the final phase of human testing, and working so that the World Health Organization (WHO) grants the vaccine the necessary certificate. After testing the vaccine on 300 people in Brazil, it will now be tested on another 2,000 in Senegal. If all goes well, the vaccine will become the first in the world to protect against a worm. Vaccine studies began in the 1980s, when the aim was to protect cattle from parasitic infections. After decades of lack of interest from industry in developed countries and a few failed attempts, the vaccine could begin to be marketed by the end of 2025 or the beginning of 2026, says Tendler.

The disease, popularly known in Brazil as “water belly,” is closely linked to poor sanitary conditions and the lack of sewage networks and drinking water, which is why it affects the poorest countries the most. Infection occurs through the larvae of the parasitic snail eggs, which penetrate human skin. Once in the blood, the larvae transform and settle in organs such as the liver. The adult worms may end up in the veins of the intestine or bladder, leading to the characteristic bloated stomach.

The vaccine contains the Sm14 protein, present in the Schistosoma. These proteins are key because they transport the necessary fats that guarantee the survival of the parasite. But the vaccine protein is modified and prevents the transport of these fats, thus preventing the proliferation of the parasite. The discovery could dramatically change the landscape in dozens of countries where the disease is currently treated with drugs. Although it has a low mortality rate, schistosomiasis drastically lowers quality of life. It affects, for example, children’s learning in schools and the work performance of young adults, explains Tendler.

According to the WHO, it is estimated that every year 200 million people are infected with the parasite, while another 800 million live in high-risk areas. In Africa, it is present in 74 countries, and in Latin America, 95% of cases are reported in Brazil. Worldwide, it is the second most socioeconomically devastating parasitic disease, second only to malaria.

The vaccine is the result of a collaboration between the Oswaldo Cruz Foundation and the U.S. company Orygen Biotechnology, but it has been developed entirely in Brazil. All the technology used is Brazilian, and so are the patents, Tendler proudly points out. The researcher stresses that while Brazil does not have the same financial resources for research as Europe or the U.S., it has much more in-depth knowledge of tropical and parasitic diseases. In her opinion, Shistovac will be a landmark vaccine.

“It is a highly sophisticated vaccine, and it breaks a paradigm that continues until today,” she says. “We hope that it will open the way for other antiparasitic vaccines that are off the radar of the big industry because there is no market for them in countries in the northern hemisphere and are therefore not considered a priority.”

The organizations involved in the development of the vaccine have promised to commercialize it at a low cost so that it can be accessed where it is most needed. It will fit within what the WHO defines as a “humanitarian” vaccine.

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