mosquito's larva in water. Isolated in studio backgrou

Despite major breakthroughs in medicine over the years, some diseases remain mass killers and few cast a longer shadow than malaria, particularly in Africa where it has claimed millions of lives.

Key to tackling the disease has been prevention and now the world’s first vaccine against malaria will be introduced in three countries – Ghana, Kenya and Malawi – starting in 2018.

The RTS,S vaccine trains the immune system to attack the malaria parasite, which is spread by mosquito bites, and needs to be given four times – once a month for three months and then a fourth dose 18 months later.

One of the big challenges is that the breakthrough has been achieved in clinical trials but it is not yet clear if it can be replicated in countries where access to healthcare is limited.

That is why the World Health Organisation (WHO) is running pilots in the three countries to see if a full malaria vaccine programme could be started.

Dr Matshidiso Moeti, the WHO regional director for Africa, said: “The prospect of a malaria vaccine is great news. Information gathered in the pilot programme will help us make decisions on the wider use of this vaccine.

“Combined with existing malaria interventions, such a vaccine would have the potential to save tens of thousands of lives in Africa.”

The pilot will involve more than 750,000 children aged between five and 17 months. About half will get the vaccine in order to compare the jab’s effectiveness. In this age group, the four doses have been shown to prevent nearly four in ten cases of malaria, much lower than approved vaccines for other conditions.

It also cuts the most severe cases by a third and reduces the number of children needing hospital treatment or blood transfusions but the benefits fall off significantly without the fourth dose.

Ghana, Kenya and Malawi were chosen because they already run large programmes to tackle malaria but despite huge progress, there are still 212 million new cases each year and 429,000 deaths. Most of the deaths are in children.

The pilots are being funded by Gavi, the Vaccine Alliance, the Global Fund to Fight Aids, Tuberculosis and Malaria, Unitaid, the WHO and GSK.

Dr Seth Berkley, the chief executive of Gavi, said: “The world’s first malaria vaccine is a real achievement that has been 30 years in the making. Malaria places a terrible burden on many of the world’s poorest countries, claiming thousands of lives and holding back economies. These pilots are crucial to determining the impact this vaccine could have on reducing this toll.”

Kenya is an example of what can be achieved but also of what challenges remain in a country where 70% of the 46 million people are at significant risk from the disease.

The preventive measures are led by the country’s Ministry of Health. In the coastal areas near the Indian Ocean and the Lake Victoria region, for example, malaria prevalence hovers around 8% and 27% respectively. Here insecticide-treated bednets are the primary preventive tool whereas indoor spraying with insecticides is targeted towards selected areas with high transmission around Lake Victoria.

In the capital city of Nairobi, fewer than 1% of people harbour the parasite that causes malaria. The presence of the parasite is also low in the country’s arid regions, where it can peak at around 3% following heavy rains.

Kenya’s malaria response in these areas focuses primarily on effective diagnosis and treatment. Beginning in 2006, the distribution of insecticide-treated bednets in high-risk areas was carried out initially for pregnant women and children under the age of five years, who are at the highest risk of contracting the disease. In 2011, distribution was widened.

Another preventive measure targets pregnant women near Lake Victoria and along the coast by giving them preventive doses of an antimalarial drug.

Taking a national approach is seen as crucial. Many Kenyans live in areas with low malaria transmission, such as Nairobi, so have little or no immunity to the disease and can easily become infected when they travel to high transmission areas.

Often, they start to develop symptoms after returning home to low-transmission areas so health promotion messages are broadcast nationally so that residents can learn how to limit their exposure and, if they do fall sick, recognise the symptoms so that they can be diagnosed and treated.

Such efforts have had an impact. Countrywide, malaria prevalence dropped from 11% to 8% between 2010 and 2015.

Progress has not been uniform. In 2015, the 8% prevalence in the endemic coastal region of the Indian Ocean was twice what it had been in 2010 although the reasons are unclear.

And in western Kenya, around Lake Victoria, malaria mosquitoes have started to develop resistance to the pyrethroid insecticides used in the two biggest malaria prevention tools, bednets and indoor spraying.

The World Health Organisation conducted research to see if mosquito resistance was undermining the preventative work. Carried out with the support of the Bill & Melinda Gates Foundation, the five- country study, including Kenya, provided reassuring results.

Dr Tessa Knox, a scientist working in the WHO Global Malaria Programme, said: “The significant reductions in malaria in the past decade and a half can be largely attributed to massive scale-up of interventions using insecticides.

“The overall conclusion was that treated bednets continue to be effective against malaria in areas where we have witnessed development of moderate levels of resistance to pyrethroids, the insecticide class used in nets.”

Currently, other new tools are being investigated and new classes of insecticides for use in bednets and sprays are being developed.