First malaria vaccine hits 1 million dose milestone — although it has its shortcomings

Ari Daniel

May 13, 2022 / 10:23 am

caption: A health worker vaccinates a Kenyan child with the world's first malaria vaccine. Kenya has given at least one dose to 300,000 children so far.

Earlier this week, Dr. Kwaku Poku Asante of Ghana got the phone call he consistently dreads. It was his son's school. His child had a fever. "I'm not sure whether it's malaria," he says, "but I'm troubled."

Asante's son is 14, so he's not in the high risk group of children ages 5 and younger. Still, parents in much of Africa are terrified by a youngster's fever, which may signal malaria.

The disease defines much of Asante's professional life too, as director of the Kintampo Health Research Centre. "I've witnessed many, many, many, many children at the hospital," he says. "Sometimes [they] come in convulsing. Sometimes they come in with severe anemia. Sometimes they come with vomiting."

And sometimes these children die. In 2020, the World Health Organization counted almost a quarter billion cases of malaria in kids and adults, primarily in Africa, resulting in 627,000 deaths. For years, the best protective measures have been preventative — insecticide-treated bed nets, antimalarial pills, shutting windows at night and reducing mosquito habitat.

"With all these interventions, there came a time when we plateaued," says Dr. Rose Jalang'o who works with the National Vaccines and Immunization Program at the Ministry of Health in Kenya. "At that point, we needed new tools to further reduce the burden of malaria disease."

Just such a new tool arrived last fall when the WHO authorized a malaria vaccine — the first ever against a parasitic disease — to be rolled out in Ghana, Kenya and Malawi. And now it's hit a milestone – 1 million kids have received at least one dose as of April.

The timing of the vaccine launch is critical. During the pandemic, the mosquito-borne disease saw a surge in cases and deaths.

"Wow, this is a total game changer," says Jalang'o, who coordinates Kenya's malaria vaccination effort.

The vaccine has been a long time coming. It's taken over 30 years to develop, in part because "the malaria parasite is so complex," says Dr. Mary Hamel who leads the malaria vaccine team at WHO. Its 5,000 or so genes (compared to only about 30 for SARS-CoV-2) have allowed it to evade our immune system through a variety of adaptations. The vaccine combines an immune stimulant and a protein that "completely coats the outer membrane of the first stage of the malaria parasite, which is called the sporozoite," explains Hamel.

There are concerns about the effectiveness of the new vaccine – and its demanding schedule. It requires 3 or 4 doses by age 2 – a challenge for parents. What's more, the vaccine only reduces hospital admissions of severe malaria by 30%, and there's a wide margin of error on that figure. With three doses, efficacy can wane, although children do gain a measure of protection at a vulnerable age.

But that benefit can be extended. A fourth dose, says Hamel, extends the protection up to age 3 1/2 or even 4. Furthermore, vaccinating before the season of high malaria transmission provides that added protection at a crucial time.

"Having a malaria vaccine has the potential of reducing the deaths associated with malaria, so I think it's a really big deal," says Jalang'o. She says that community members have told her that their children are contracting malaria less: "For example, a mother tells you that a child who's been vaccinated might have only 1 or 2 episodes of malaria in a year compared to 4 or 5 cases in the past."

"You know, it's not perfect," says Dyann Wirth, a geneticist at the Harvard T. H. Chan School of Public Health. "Would I like a vaccine that's 100% effective and easily given in one dose? Absolutely. But that's not the reality." Wirth chairs an independent malaria advisory group at the WHO and observes, "The vaccine shows some protection. I think not using it would not be justifiable. It is important that it be available to the populations that can benefit."

In addition, health professionals on the ground say this vaccine isn't intended to replace other measures like bed nets. It's one more layer of protection.