Malawi and the World Health Organization are rolling out a new malaria vaccine for young children that backers say will reduce deaths from the mosquito-borne disease.
The first malaria vaccine has been given to more than one million children in Ghana, Kenya and Malawi so far. It could save tens of thousands of lives when it is rolled out more widely, and a second vaccine is also in development.
We look at the history of malaria advancements and Wellcome’s involvement in recent progress.
In 2020, nearly half of the world's population was at risk of malaria – a life-threatening disease caused by parasites that are transmitted to humans via the bites of infected female Anopheles mosquitoes. The percentage of people at risk could increase significantly because of climate change.
Fever, chills and a headache – the first symptoms of the disease – usually appear 10 to 15 days after a person is bitten by an infected mosquito. The symptoms can be mild and difficult to recognise as malaria, sometimes until it is too late. Left untreated, P. falciparum malaria – the most deadly and prevalent parasite on the African continent – can cause severe illness and even death within just 24 hours.
According to the World Health Organization’s (WHO) latest World Malaria Report, there were an estimated 241 million malaria cases and 627,000 malaria deaths worldwide in 2020. This represents about 14 million more cases in 2020 compared to 2019, and 69,000 more deaths.
Sub-Saharan Africa carries the highest number of cases, or disease burden. These account for about 95% of all malaria cases and 96% of all deaths in 2020. Children under five made up around 80% of those deaths.
Some people are at greater risk of disease. Infants, the under-fives, pregnant people, people with HIV/AIDs, and mobile populations, like migrants, who have low immunity and move into areas with high transmission, are all more likely to contract malaria, and to suffer severely.
However, it remains a largely preventable and curable disease, and several recent advancements – including the development of the first malaria vaccine – could save the lives of hundreds of thousands in the future.
How is malaria prevented and treated?
Impressive progress has been made in reducing the burden of disease – and fatalities caused by it – thanks to the development of several malaria treatments and preventions.
Antimalarials and insecticides
As early as 1820, two French chemists isolated quinine – a treatment for malaria still used today – from the bark of the cinchona tree.
Antimalarial drug chloroquine (a synthetic analogue with the same mechanism of action as quinine) and insecticide DDT were pivotal to the execution and at least initial success of the WHO’s Global Eradication of Malaria Campaign in 1955.
Research found that mosquito vectors – or carriers – of malaria rested inside houses after taking a blood meal. This made them susceptible to control through the indoor residual spraying of DDT. While it dramatically reduced transmission, the cost of spraying, and the environmental concerns about using residual insecticides, saw these programmes halted in most endemic countries that did not have the resources to continue them. When they stopped, transmission rates bounced back to the same levels as before the spraying programmes were launched.
Similarly, drug resistance to antimalarials like chloroquine that were used in mass drug administration (MDA) programmes – in which every member of a defined population is given the treatment at the same time and often intervals – impacted the efficacy of the drug.
Artemisinin and bed nets
In 1972, artemisinin was discovered by Chinese scientist Tu Youyou, who won a Nobel Prize for the discovery. Derived from the extracts of sweet wormwood plant (Artemisia annua), the drug was found to be a cheap and effective remedy for even highly drug-resistant strains of the disease. Early clinical trials on artemisinin derivatives were conducted in Thailand led by Nick White, François Nosten and Arjen Dondorp, and in Vietnam by Tran Tinh Hien and Jeremy Farrar, followed by extensive trials in Asia and Africa, including trials of artemisinin-based combination therapies.
After decades of independent randomised clinical trials and meta-analyses, artemisinin combination therapies (ACTs) were recommended by the WHO in 2006 as the first-line treatment against malaria. In the 1990s, the introduction of bed nets soaked in insecticides prevented thousands of deaths, particularly of the babies and young children who slept under them. When mosquitoes try to bite, the netting blocks them and the insecticide coating kills them. Insecticide-treated bed nets are a highly effective tool for protecting against malaria. Between 2004 and 2019, these nets averted an estimated 68% of malaria cases in sub-Saharan Africa.
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