Malaria is humanity’s curse. It is among the oldest of human diseases, infecting our earliest ancestors, influencing our recent evolution, and causing an estimated half of all deaths since the Stone Age. Today, nearly half of the world’s population is at risk from malaria – it kills more than 400,000 people a year, most of them in Africa, where a child dies every two minutes from the disease. But now hopes have been raised of an end to the scourge: the first malaria vaccine is being rolled out in immunisation programmes in Malawi, Ghana and Kenya.

The new vaccine has been developed by GlaxoSmithKline with the support of the Bill & Melinda Gates Foundation, and others including the World Health Organization (WHO) and Gavi, the global vaccine alliance. It took 32 years of research, and cost more than $700m (£552m).

Trials show it to be just 40% effective at preventing the disease over four years. That’s about as effective as influenza vaccine, but considerably less than the 97% effective diphtheria vaccine. And yet, it may well be the most significant win in our war with malaria for several decades, preventing many thousands of deaths and reducing the great social and economic burden that comes with experiencing or caring for someone with chronic sickness. //

However, it is in sub-Saharan Africa, where it first evolved, that the disease has proved most entrenched, historically killing half of children before the age of five. It is thought that malaria first reached epidemic proportions there with the advent of agriculture (and so, land-clearance) on the continent, around 4,000 to 5,000 years ago – there are references to malaria in Sumerian and Egyptian texts dating from 4,000 years ago. //

So to combat each new infection, a human host must mount a new and “strain”-specific immune response to each antigenically distinct parasite in that mosquito bite, as well as the new antigens that arise during the course of the infection. Because of this, a single malarial infection can be prolonged over many months to years. Only when a sufficiently wide spectrum of parasite strains has been experienced is any immunity achieved. //

Historically, this protected Africans from colonial expansion. Europeans arriving on the continent died in such great numbers that the coast of Sierra Leone was known as the White Man's Grave. Malarial mortality rates exceeding 50% per year of contact were the norm on the West African coasts. And, despite the great cost of achieving immunity, it is readily lost – several months without reinfection are enough to leave an individual vulnerable to the full impact of malaria. //

Caring for sick relatives and being unable to work because of fevers traps households in poverty – economists calculate that 1% negative growth each year in Africa over the last half a century can be attributed entirely to malaria. Malaria is a disease of poverty but also a disease that impoverishes. //

The licencing of the first proven malaria vaccine, called RTS-S, adds to our defensive arsenal and marks a significant step in the battle against the disease, enabling hopes of eradication to be raised again. The vaccine exposes the body to one of the most widely used antigens on the sporozoites, which are only in the blood briefly before secreting themselves in the liver.

Nevertheless, the hope is that by getting the immune system to attack this stage, the deadly febrile merozoites stage will be avoided in the blood. During its long development, a vaccine against hepatitis B was created, which produces a highly effective immune response, so the malarial researchers decided to add this to the sporozoite antigen in order to prime the immune system. It worked – early trials found it was 87% effective at eliminating the sporazoites.

The problem is if just one sporozoite escapes the liver and enters the blood phase as a merozoite, it has the capacity to reproduce exponentially and produce malaria. For this reason, clinical trials found that the vaccine is only 50% effective at preventing malaria for a year after inoculation, and this falls to 40% after four years. //

Lode Schuerman, director of global medical affairs at GSK, who has spent the past decade developing the vaccine. “It should be feasible to eliminate malaria.”

The danger, he warns, is in selecting interventions that reduce the disease incidence in some areas, but allow it to come back with deadly power against those with no immunity. “Knowing the parasite, I would use everything we have to once and for all address this burden,” he says. //

Several other vaccines are also in the pipeline, including one that uses the whole sporozoites (irradiated for safety) and must be injected into a vein, but is 100% effective in laboratory trials – it will enter clinical trials next year on the island of Bioko of Equatorial Guinea.