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Are we finally faced with a definite malaria vaccine?



According to the WHO, malaria causes 435 000 deaths annually, 60% in children under five in sub-Saharan Africa. There are several times that, as a teacher and researcher, it is possible to explain to the students after nearly thirty years of learning about parasitology and parasitic diseases, which finally has an effective and accessible vaccine, perhaps at a reasonable price, for one of the diseases that cause the main causes for morbidity and mortality worldwide.

Dr. Elena Gomez Diaz, from the Institute of Parasitology and Biomedicine Lopez-Neyra, spoke about this in a recent article. With malaria we are facing organisms for which the way we were supposed to make vaccines is no longer useful. Viruses and bacteria have simpler structures and cycles, but parasites are something else, and the technology that has been used so far does not seem to work.

Plasmodium spp. is a parasite with a complex biological cycle with several stages (sporozoites, hepatic merozoites, and gametocytes) that develop in different hosts. The parasite is changing enough to require a vaccine for each phase.

During the twentieth century, malaria caused more losses among the troops of missions carried out in endemic regions than bullets. The first attempts to develop a vaccine date back to 1942 in the middle of World War I, when two researchers from the Pasteur Institute in South India used weakened sporozoites from the malaria parasite that struck birds and achieved a 21% reduction in mortality. Twenty-five years later, Nussenzweig reported in Nature his work with X-rays plasma-mediated plasma spores, which produces partial immunization in mice.

A step towards immunization of people began in the 1970s with the inoculation of sporozoites of irradiated mosquitoes among volunteers who were protected from malaria between three and six months. Work with volunteers continued throughout the 1980s; sporozoids appear to be a crucial stage, but immunization has been lost over time and definitive conclusions have been far from over. Still they are.

In the 1990s, the study by Manuel E. Patarrojo focused on the use of parasite proteins that led to the synthetic peptide SPf66 and what seemed to be a new hope for immunization that worked for monkeys. The so-called Colfavac (collective vaccine against Falciparum) was a donation of WHO, tested on people in different countries.

However, despite a good prospect in Phase I trials, in which 75% efficiency and good tolerance were observed, Phase II and III studies did not retain protection in African children (2%), variable protection in Asia and low protection in the South America (28%). In addition, this initial efficiency was lost over time. Subsequent studies have recommended new studies with new formulations of SPf66.

Patarroyo did not try to create a universal vaccine, but to get a universal method for developing any vaccine. A much more ambitious goal.

So far, in the millennium, thanks to funding from the pharmaceutical company GlaxoSmithKline and the Bill and Melinda Gates Foundation, with the approval of the European Medicines Agency, RTS, C / AC01 was developed. It is a vaccine based on two plasmodium surface proteins capable of activating the human immune system, registered as Mosquirix®.

But getting here was not easy. In 2012, after acting in children aged 5 to 17 months reduction of cases of severe malaria to 50%, the effectiveness of the RTS vaccine, S dropped. Tests carried out in 2015 showed that with the fourth dose of reinforcement the results improved. It continued to recommend the use of the vaccine together with other control measures, such as drugs or mosquito nets, especially in high-transmission areas.

It should be borne in mind that tropical diseases affect mainly people living in poorer regions of developing countries. His research has no over-economic interest in pharmaceutical companies because it is a market that can not pay the cost of treatment.

The pharmaceutical industry is oriented, above all, on chronic diseases treated with highly profitable drugs. There is an urgent need to increase initiatives to promote research and development of drugs for so-called "poverty disorders". Governments play a key role in reducing health inequalities and guarantee access to the best available therapies.

Africa, with high population and economic growth, is a growing potential market for vaccines. There are already recent studies that are aimed at activating an investment in vaccine production in Africa, seeking a way to make it available to the majority of African governments and investors.

Drugs and vaccines as a business have always been in the spotlight, but beyond the benefits of their sale, the investment in vaccines implies long-term savings in the health costs arising from this disease.

In 2014, the results obtained in Malawi, comparing the economy of the RTS vaccine, S / AS01 and the use of mosquito net, indicated the vaccine as a very profitable component of the country's future malaria control programs.

Despite this, the research on the malaria vaccine has stagnated for a long time. The project was suspended when the pharmaceutical company GlaxoSmithKline had already invested nearly $ 300 million with almost no results, leaving the vaccine stored in a shelf. The use of new study techniques and public-private partnerships that shared costs led to new advances.

Thus, the consortium established between the PAT Malaria Vaccine Initiative (Gates Foundation), GlaxoSmithKline and the Walter Reed Army Research Institute, which has the necessary infrastructure to produce large vaccines in a short time, has continued to work. Various ministries of health from African countries and many other national and international partners and organizations such as GAVI-Vaccine Alliance, Global Fund and Unitaid have joined.

All this collaboration has resulted in the development of a global vaccination program that will soon begin in Malawi and will extend to other African countries.

We already know that the RTS, S vaccine is intended for use in children, not in adults, and that its effectiveness is not 100%. We know that it is necessary to receive four doses of memory, because effectiveness decreases over time. However, the logistics of how to administer it is very complex and we do not know the price of the vaccine production or the price at which it will be placed. The pharmaceutical company plans to bring it to the market at a cost plus 14%, which it intends to allocate for researching new drugs against this disease.

Despite this, it will be very useful. It will save thousands of lives and will be a tool for controlling malaria, added to the basic set of measures recommended by WHO in preventing the disease, which includes the use of insecticide-treated mosquito nets, early diagnosis and drug use. for the treatment of malaria.

But researchers are already accustomed to taking the good news with caution. It is a step in the fight, nothing new in the history of the disease, full of failures and successes that have become partially over time.

Even so, it is a reason for a celebration for those who have been working for so many years, taking short steps in the right direction and, above all, for the people they need. It is necessary to invest, to examine and to work on diseases that look remotely to us. For justice, for ethics and for social responsibility.

Consuelo Giménez Pardo: Professor of Tropical Diseases and Global Health of UAH, Director of Master's Degree in Health Humanitarian Action, University of Alcalá


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