Almost half of the World’s population is at risk of malaria according to WHO, with an estimated 212 million cases in 2015 and 429,000 deaths. There is no known cure for malaria and taking a lot of preventative medicines is not always easy for people in affected countries. Here we investigate a potential new vaccine against the parasite.
Plasmodium falciparum (P. falciparum) is the deadliest of the 5 protozoan Plasmodium (parasites) which can carry malaria in humans. Malaria is a tropical disease found in more than 100 countries, spread by mosquitoes and can have symptoms such as a fever, headache, vomiting, muscular pain and diarrhoea. The parasite is specifically carried by female Anopheles mosquitoes, which bite individuals and enable the parasite to enter a person’s bloodstream. Currently the only form of prevention is vector control (i.e. mosquito nets, insecticides, and a course of antimalarial drugs). The parasite has a 12 stage life cycle but it is the release of sporozoites (during the mosquito stage) which are considered to be the infectious agent. Most worryingly, drug resistance is increasing and thus there is a demand for new anti-protozoan drugs.
My MSc research project at the University of Leeds looked at plasmodium falciparum. We were designing drugs which could possibly inhibit the disease. It was a tough task but a worthy cause. Unfortunately I did not cure malaria, but a new vaccine created by Sanaria has shown 100% protection against malaria in laboratory testing. The vaccine is called PfSPZ. They hope to use PfSPZ “to prevent malaria in individuals and, in combination with other malaria control measures, to halt transmission of, and eliminate malaria from communities”.
The news of PfSPZ’s effectiveness has been known for at least 2 years (2017) and so far, Sanaria have done small trials, testing the vaccine in a total of 2511 people from Europe, America, Africa and Asia, from infants to the elderly. Follow this link to see live updates on their trials: LINK. How does the new vaccine work? Standard vaccinations that we are given throughout our lives protect us against numerous viruses by giving us a small amount of the infectious agent either alive (i.e. attenuated) or dead. This triggers a small immune response which our bodies remember, so if we encounter the infectious agent again we remember how to fight it effectively. PfSPZ uses a new method. Obviously the infectious agent is a parasite, not a virus which is usually prevented through the use of vaccinations. PfSPZ is instead made with sporozoites, the infectious stage mentioned before. Sanaria isolates and purifies billions of sporozoites from farmed mosquitoes, and uses the entire parasite in the vaccine. To date, other parasitic vaccination trials use only part of the parasite. By using the entire parasite, a strong immune response occurs and the individual is then protected. Healthy volunteers have had complete protection after receiving the vaccine.
Why the hype now? Well, it has just been announced that a large scale clinical trial is set for 2020. The trial will take place on the island of Bioko, off the coast of Equatorial Guinea and will involve 2,100 people between the ages of 2 and 50. This trial should provide efficacy (i.e. produces the desired effect) and safety data to enable regulatory approval of the vaccine to be tested on a larger population of the island (100,000 people). Are there possible problems? Researchers have already highlighted a few potential issues that could occur during the trial: (1) some participants may have weaker immune systems if they have already been exposed to malaria in the past (which is likely), (2) the local strains of malaria may differ from those tested in the lab, rendering the vaccine potentially useless. Despite this, conventional measures such as nets, anti-malarials and sprays, have already helped the small island. Rates of malaria have dropped from 45% to 12.5% in 5 years, so even if PfSPZ is not 100% effective, it should help the incident rate drop further.
Malaria can be a devastating disease, spread in a manner which is very hard to control in developing countries with poor water sanitation. Current preventative measures have their faults; nets can get holes, spray isn’t pleasant, and it can be hard to ensure that people take tablets correctly over the course. A vaccination however, could prove very effective as can be seen with numerous vaccination programmes before (e.g. small pox, HPV, etc.). If these trials are successful, it will be interesting to see how the next stage progresses and potentially see the dramatic decline, or even eradication of malaria worldwide.