Mosquirix
The most important news in healthcare: Friday, October 8th
Moderna recently announced plans to start a vaccine plant in Africa amidst an ongoing debate that big pharmaceutical companies should be doing more to achieve vaccine equity throughout the world during a pandemic. While many have been focusing on global COVID-19 vaccine access, there’s a far deadlier disease on the continent with a massive vaccine announcement this week. The World Health Organization just announced a rollout of the world’s first malaria vaccine. Read on to learn about the development process, the vaccine’s efficacy, and about its potential impact.
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GLOBAL HEALTHThe WHO to roll out the world’s first malaria vaccine
The pulse:
The World Health Organization has approved the world’s first malaria vaccine. It could prevent deadly infections in hundreds of thousands of children a year.
The need:
Malaria is a parasitic, mosquito-borne blood disease that can be fatal. Though it’s unlikely for people to become infected in the US, you may have been told to take prophylactic medication if you’ve ever travelled to parts of the world where malaria is prevalent.
Malaria actually used to be endemic to much of the southern US. It was eradicated in 1949 through widespread use of insecticides (sometimes sprayed from aircrafts), window screens, and targeted destruction of mosquito breeding sites. The disease still remains endemic in much of sub-saharan Africa, a fact which is often attributed to weaker infrastructure that cannot support similar measures, as well as struggling health systems that cannot keep up with the sheer numbers of infected individuals.
Of the 229 million cases of malaria each year, about 94% of them are in Africa. Even more devastatingly, children are often the hardest hit victims. More than 260,000 African children died from the disease in 2019 alone.
Why has it been so hard to develop a malaria vaccine?
Decades of research and funding have been poured into the development of a malaria vaccine. There have been over 100 candidate vaccines tested in clinical trials over the years, all of which previously failed to prove efficacy. That’s because the organism that causes malaria, the Plasmodium species, goes through a complex life cycle and is adept at evading the immune system. The multiple immunologically distinct life stages make it hard to effectively block transmission.
For example, while high antibody levels (part of what’s called the humoral response) have been shown to be effective against the blood stage and sporozoite parasites, they are not as effective against the parasitic stage prominent during liver infection. This allows these liver stage organisms to escape antibody-focused therapeutics. To effectively target organisms in the liver, a vaccine which produces cellular immunity is needed, meaning the vaccine has to induce T-cells (a type of immune cell) to become active and mount an attack. It’s a tall order to get a robust cellular and humoral response to effectively target the various life stages of the Plasmodium organism. Until now, it couldn’t be done.
WHO Director-General Tedros Adhanom Ghebreyesus, who started his career as a malaria researcher, announcing the approval of Mosquirix.
The development process:
GlaxoSmithKline (GSK) has been working on its candidate, RTS,S or more simply, Mosquirix, for nearly 30 years. The vaccine, the world’s first for a parasitic disease, is designed to be given in four doses. The first dose should be given ~6 months of age, with the next two doses given in monthly intervals after that. The final and fourth dose is scheduled to be given 18 months after the first, a logistic that has raised eyebrows over feasibility (we’ll get to that). In November 2016, the WHO announced a pilot program to roll out the Mosquirix vaccine in Ghana, Kenya, and Malawi.
The pilot program:
The pilot program was designed to analyze the real world efficacy of the vaccine and the feasibility of delivering a four-dose vaccine in countries with weak health infrastructure. The results have been promising so far — over 800,000 children have already received Mosquirix. The data showed about a 40% reduction in contracting malaria and about a 30% reduction in serious illness leading to hospitalization. Admittedly, its efficacy rate is by no means a knockout and is actually quite modest compared to most other childhood vaccines. Still, given the overwhelming burden of disease, even a vaccine with modest efficacy could provide significant relief. One modeling study showed the vaccine could prevent the deaths of 23,000 children per year.
Most importantly, the pilot program helped assuage some concerns raised about the vaccine, such as the difficulties of administering a four-dose vaccine or whether it would reduce the use of other anti-malarial measures such as bed nets. The trial showed effective delivery of all doses through a network of child health clinics and that the vaccine did not negatively impact other anti-malarial tools.
The coming rollout
So far, GSK has committed to producing 15 million doses annually up to 2028, at cost of production plus up to a 5% margin. More doses will certainly be needed — a WHO study projected vaccine demand would be 50-110 million doses annually by 2030 in areas with moderate-high disease transmission.
A successful roll out will depend on NGOs such as GAVI, the Vaccine Alliance, to help fund and distribute these doses. Dr. John Nkengasong, Director of the Africa Center for Disease Control and Prevention urged donors not to play a zero-sum gam "where we fund COVID vaccines and neglect malaria vaccines".
Bottom line it for me:
The WHO’s historic approval of a malaria vaccine could change the public health landscape in much of sub-saharan Africa. Successful roll out will rely on a firm commitment from both global donors and pharmaceutical companies to focusing on malaria — not an easy task with an ever-present global pandemic still raging.