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13 October 2021

We should be optimistic about the malaria vaccine – but not necessarily for the reason you think

The WHO-approved jab could prevent up to 4.3 million malaria cases and 22,000 deaths each year. But we can do better.

By Stuart Ritchie

One of the best possible things we could do in the world would be solving malaria. The disease – which isn’t caused by a virus or a bacterium but by a family of microscopic parasites known as plasmodia, borne by a particular genus of mosquito – has a uniquely devastating toll in some of the world’s poorest countries, and seems to have been with us since ancient times.

That’s why the news last week (7 October) that the World Health Organisation (WHO) has given its approval to a malaria vaccine was so exciting. Or, at least, sort of.

The vaccine’s approval is both news and not news at the same time, as I’ll explain. First, though, let’s just be clear how grim the challenge of malaria is. It’s not that a very high proportion of people who catch the disease die – it’s just that an awful lot of people catch it: 229 million in 2019 (the last year for which we have data). So even with a low-seeming fatality rate – around 0.2 per cent – it translates to a truly tragic number of deaths: 409,000 that same year, of which two-thirds (274,000) were of children under five.

Even leaving aside deaths, the disease and its flu-like symptoms have dreadful effects: an estimated 822,000 babies in 2019 were born with low birthweight due to their mothers being infected with malaria while pregnant, and already fragile economies in sub-Saharan Africa are further held back by its effects on people’s ability to work – to the tune of something like $12bn per year.

There has been significant progress against this devastating disease in recent years. The death rate from malaria is substantially lower than it was at the turn of the century. If the mortality rate had stayed the same as it was in 2000, the WHO calculates that there would have been an additional 7.6 million deaths in the subsequent 19 years.

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One reason for the declining death rate is that we’re now much better at malaria prevention. Insecticide-soaked bed nets, which protect people from the mosquito bites, have become far more widely used over time. In 2000, essentially zero homes in sub-Saharan Africa had such a bed net. Now, something like 70 per cent have at least one. Much of this is due to the heroic work of groups like the Against Malaria Foundation, which is among the most effective charities in the world in terms of lives saved per pound spent.

But even with more bed nets, and better malaria-preventing drugs, we still have the hellish figures I quoted above. That’s where the vaccine comes in.

There are a whole host of candidate vaccines for malaria, which are at various stages of testing. Some focus on the parasites in the bloodstream, some on stopping transmission (not from person to person but from person to mosquito, and thus from mosquito to person again), and some are aimed at stopping infection in the first place. The vaccine that has just been approved, known as RTS,S (or by its brand name Mosquirix), is one of the latter kind: it blocks the parasite from invading the liver, where it changes and multiplies before entering the blood.

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The sense in which this isn’t really news is that the vaccine has been around since the 1980s, and we’ve had the data from a phase III clinical trial – where its efficacy was tested in large numbers of people – since 2015. The WHO has approved it now because of pilot trials in Ghana, Kenya and Malawi, which demonstrated that giving four doses to children was feasible and cost-effective.

The phase III trial showed that the vaccine reduced malaria infection by 46 per cent in children and 27 per cent in infants. This might seem a bit limp, especially when we’re used to hearing about prevention rates from mRNA Covid vaccines in the 90 per cent range – and also compared with other childhood vaccines, like the MMR, which is 97 per cent effective against measles. But a modelling study from last year still estimated that, given some assumptions about the rollout of the jabs, the RTS,S vaccine could prevent up to 4.3 million malaria cases in infants, and 22,000 deaths, each year.

The WHO’s own target is to have a vaccine with over 75 per cent efficacy against malaria by 2030 – and clearly RTS,S falls far short. Don’t despair though: while we’re rolling out RTS,S in sub-Saharan Africa, other vaccines are on the way. This April, Oxford University announced that its malaria vaccine, called R21, showed a far more promising 77 per cent efficacy in children in a phase II trial (a smaller, more preliminary study).

So, despite the fanfare, and although it does represent genuine and exciting progress against malaria, the approved RTS,S vaccine is likely only a stopgap in our ultimate goal of eradicating the disease altogether. It’s now our responsibility to make sure that other, more effective vaccines get over the regulatory hurdles as quickly as possible – and maybe even get emergency approval, like the Covid vaccines. The pandemic has shown us that it’s possible to cut down the usual frustratingly long process of drug approval if the situation is really urgent. If a quarter of a million dead children every year isn’t an emergency, then what exactly is?

[See also: How bad is the winter flu and will it cause a winter lockdown?]