RTS,S Malaria Vaccine Shows Early Impact in Cameroon, But Fourth-Dose Drop-Off Threatens Durability of Protection
核心洞察
More than two years after Cameroon became the first country to integrate the RTS,S malaria vaccine (搜索) into routine immunization, health workers report reduced severe illness and emptier pediatric wards.
First-dose coverage rose from 66% to 68% between 2024 and 2025, but fourth-dose coverage stood at just 25% as of 2025, mirroring a drop-off seen in pilot programs across Ghana, Kenya, and Malawi.
The WHO-recommended four-dose regimen is considered essential for prolonged immunity, yet parents and health workers often forget the booster given around age two, months after the third dose.
YAOUNDE, Cameroon — Rain had turned the dirt road into thick mud, but Mabel Djoumessi kept walking with her 9-month-old son, Kenfack, strapped to her back. His malaria (搜索) vaccination appointment at a clinic in central Cameroon was too important to miss. For decades, millions of children across Africa have fallen sick from malaria, one of the continent's deadliest diseases for the young. But Kenfack has never had it — a feat his mother attributes to the recent arrival of a malaria vaccine.
"My other children who have never taken the vaccine frequently fall ill," Djoumessi said, sitting with other women cradling babies at Soa District Hospital.
More than two years after Cameroon became the first country to incorporate the RTS,S malaria vaccine (搜索) into its routine immunization program, health workers say it is reducing severe illness. But they worry that too few children return for the fourth and final shot — the booster dose that the World Health Organization says is essential to prolong immunity, given months after the other doses.
A Four-Dose Regimen Under Strain
Malaria (搜索) remains the leading cause of hospital consultations and admissions in Cameroon, one of 11 countries accounting for about 70% of the global malaria burden, according to the WHO. The country recorded an estimated 7.6 million malaria cases and 11,700 deaths in 2024. Data from Cameroon's National Malaria Control Program shows health facilities recorded a drop in cases in 2025, with 33,000 fewer than in 2024.
However, some have cautioned against attributing the decline solely to the vaccine. "Isolating the specific impact of malaria (搜索) interventions requires modeling, and we do not yet have a model to quantify the vaccine's sole contribution," said Dr. Bomba Amougou, head of prevention at the National Malaria Control Program. "Therefore, it is accurate to say that the vaccine has contributed to the reduction in cases and deaths, rather than being the exclusive cause."
The WHO recommended the RTS,S vaccine for wider use in 2021 after pilot studies in Ghana, Kenya and Malawi found it reduced deaths among eligible children by 13%. In separate clinical trials in several African countries, both RTS,S and the newer R21 vaccine reduced clinical malaria (搜索) cases by more than 50% during the first year after three doses.
At Soa District Hospital, nurses said they can see the vaccine's impact. "Our pediatric wards have become empty," said Alice Tchuenmegne, a senior nurse in charge of vaccinations.
Coverage Gains — and a Stark Drop-Off
After introducing the vaccine in 42 high-burden districts, Cameroonian authorities say coverage has improved among infants eligible for the first three doses, given at six, seven and nine months. First-dose coverage rose from 66% to 68% from 2024 to 2025, second-dose coverage from 53% to 58%, and third-dose coverage from 48% to 59%, according to Amougou.
But many children never receive the fourth dose, administered around their second birthday. Coverage for the fourth dose stood at 25% as of 2025, Cameroonian figures showed.
"Parents and even health workers sometimes forget the fourth dose, particularly as it is administered long after the third, and because this is a relatively new vaccine," Amougou said. Receiving all four doses "makes the protection more potent," he added, emphasizing that vaccination must complement bed nets, prompt treatment and good sanitation.
The problem extends beyond Cameroon. In a malaria (搜索) vaccine pilot program across 158 districts in Ghana, Kenya and Malawi, coverage reached about 80% for the first shot, given at around six months of age, but dropped to 46% for the fourth dose, administered between 22 and 24 months, according to a study published last year in the peer-reviewed Malaria Journal. Researchers found that parents overwhelmingly accepted the malaria vaccine, but children missed later doses largely because of transport costs, lack of reminders, poor follow-up and competing work or childcare responsibilities.
Supply, Demand, and the Push for a Single Dose
Over 52 million doses have reached 25 high-risk African countries with support from Gavi, the Vaccine Alliance (搜索). However, the organization has said the rollout faces a "stark constraint" after sweeping foreign aid cuts by the Trump administration and others. Gavi says it is guaranteeing the supply of vaccines to cover up to 70% of eligible children in the lowest-income countries.
The lower vaccination rates are "initial teething problems that I don't think should take the spotlight away from the value of this vaccine," Gavi Chief Executive Officer Dr. Sania Nishtar said in an interview. She noted the malaria (搜索) vaccine faces the least hesitancy from parents, attributing that to their desperation to save their children from malaria deaths. As a result, there is "huge demand" from governments and communities.
Cameroon and other African countries have since launched "Big Catch-up" campaigns encouraging parents and health staff to prioritize children's vaccination. Despite the challenges with completing the malaria (搜索) vaccine doses, Gavi said Wednesday that lower-income countries vaccinated more children in 2025 — 73 million — with Gavi-supported vaccines than any year in history.
Nishtar confirmed research efforts continue toward a single-dose malaria (搜索) vaccine. "The fewer the doses of a vaccine to be administered, the higher the uptake and the easier the administration," she said.
The Economic Toll of Malaria (搜索)
For many families, preventing malaria (搜索) also means avoiding crushing medical bills. Georgette Caroline Mengbwa, a mother of three waiting for her youngest daughter's third dose, said her two older children were born before the vaccine became available. "They fall ill every two or three months, and I have to spend between $53 and $107 each time one or all of them fall ill," she said. "It's a lot of money."
Such costs are substantial in a country where the monthly minimum wage is about $76 and nearly 40% of the population live in poverty, according to official figures. Malaria (搜索) kills one child younger than 5 nearly every minute globally, the vast majority in Africa, according to the WHO and the United Nations children's agency.