ATLANTA (AP) — The quest for the world's first malaria vaccine appears to have taken a big step: A study in Africa shows experimental shots cut the risk of disease in young children by half.
The initial results from a final stage of vaccine testing were released Tuesday, and the vaccine's developers called it a milestone in helping to tame one of the world's most devastating killers.
However, the vaccine won't be available for at least three years, as crucial further testing must be completed to see how well it works in infants and how long protection lasts. Then the vaccine must be reviewed by government agencies in Europe and in individual African countries.
"We still have a way to go," Tsiri Agbenyega, lead researcher for the African study, said in a conference call with reporters.
The early results show the vaccine is only about 50 percent effective, significantly lower than the protection seen in more common vaccines. But some experts said it's a vast improvement over the current situation, and could still save hundreds of thousands of lives.
Globally, malaria kills nearly a million people annually. More than 90 percent of them live in Africa, and most are young children and pregnant women.
Scientists have been trying for decades to develop a malaria vaccine and the one tested — developed by GlaxoSmithKline — is furthest along. Without a vaccine, public health efforts have concentrated on malaria drugs and other ways to prevent infection such as mosquito bed netting and insecticides.
Those efforts have been successful: Some countries have been able to reduce malaria deaths in younger children by up to 50 percent, noted Dr. Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention.
The new vaccine targets a malaria parasite found in sub-Saharan Africa. Malaria spreads through mosquitoes, which bite people and flush malaria parasites into the bloodstream. The parasites cause bouts of high fever and can end in fatal organ failure.
In the United States, malaria has been eradicated since the early 1950s. Only about 1,500 cases are diagnosed in the U.S. each year, most of them travelers or immigrants from South Asia, sub-Saharan Africa or other places where malaria commonly spreads.
The new study — still under way — began in 2009 and involves more than 15,000 children in Burkina Faso, Gabon, Ghana, Kenya, Malawi, Mozambique and Tanzania.
Early results were released Tuesday at a malaria conference in Seattle and published by the New England Journal of Medicine.
The findings focus on about 6,000 children ages 5 to 17 months. A year after getting three doses, the vaccinated children had about half as many cases of malaria as a group that didn't get the vaccine.
Meanwhile, experts are waiting for results from a younger group — infants ages 6 to 12 weeks. That's the age when children in sub-Saharan Africa are vaccinated against other diseases. Earlier vaccination also affords earlier protection.
So far, side effects and other problems occurred at about equal rates in the vaccine and comparison groups, although higher rates of seizures and meningitis were reported in the vaccine group. The researchers think it's unlikely the vaccine was the cause, but another expert said the finding deserves more study.
The expert — Nicholas White of Thailand's Mahidol University — also questioned the release of partial results.
"It is not usual practice to publish the results of trials in pieces, and there does not seem to be a clear scientific reason why this trial has been reported with less than half the efficacy results available," White wrote in an editorial published along with the findings.
Although there are an array of vaccines against viruses and bacteria, there has never been an effective vaccine against a parasite, which is a more complicated organism. And there are five species of malaria parasites. The new vaccine is designed specifically to protect against the deadliest one, which is common in sub-Saharan Africa.
Other researchers are working on different malaria vaccines, and they anticipate a need for their work even if Glaxo's continues to succeed, said Dr. Alberto Moreno, a malaria vaccine researcher at Emory University. Another deadly species more common in Asia could replace the parasite in sub-Saharan Africa as a primary killer, he said.
"We don't know what will happen in the future," he said.
No price has been set for the Glaxo vaccine. Chief executive Andrew Witty pledged the company will price it as low as possible, based on the cost of production plus 5 percent, with all the extra money plowed into research on malaria and other diseases.
"We're not going to make any money on this project," Witty said.
The Glaxo vaccine was first created in 1987. The company has invested $300 million in the vaccine so far, and expects to spend another $50 to $100 million on it, he said.
The British drugmaker paid for the study along with the PATH Malaria Vaccine Initiative, a program funded by the Bill & Melinda Gates Foundation.
<한글기사>
세계최초 말라리아 백신 면역효과 50%
세계 최초의 말라리아 백신이 마지막 3상 임상 시험 초기 결과 50% 수준의 면역 효과가 있는 것으로 밝혀졌다.
영국의 글락소스미스클라인(GSK) 제약회사가 개발한 이 말라리아 백신(RTS,S)은 1차로 생후 5-17개월 영유아 6천명에 3차례에 걸쳐 접종하고 12개월이 지난 현재 임상적(clinical) 말라리아는 56%, 중증(severe) 말라리아는 47%의 면역 효과가 나타 났다고 AFP통신 등이 18일(현지시간) 보도했다.
이는 사하라 이남 아프리카 7개국(부르키나 파소, 가봉, 가나, 케냐, 말라위, 모잠비크, 탄자니아)의 11개 지역에서 총 1만5천460명의 아이를 대상으로 현재 진행 중이며 이날 발표된 것은 1차 결과이다. 이 임상시험은 앞으로 2년 더 계속된다.
1차 결과분석에서 나타난 면역 효과는 소아마비, 홍역 같은 다른 일반백신에 비 해 크게 미흡한 수준이지만 이 정도만 해도 말라리아 발생을 억제하는 데 크게 기여할 것으로 보인다.
박테리아나 바이러스가 아닌 기생충을 차단하는 백신이 개발되기는 이것이 처음 이다.
이 백신은 5종류의 말라리아 원충중 독성이 가장 강하고 치명적인 열대열원충(plasmodium falciparum)을 표적으로 개발된 것으로 모기에 물린 뒤 모기의 타액을 통해 말라리아 원충이 혈액으로 들어갈 때 면역반응을 촉발시켜 원충이 간(肝)에서증식하는 것을 차단한다.
이 임상시험 결과는 백신연구를 지원한 빌-멜린다 재단 말라리아 포럼의 시애틀 회의에서 발표되는 동시에 의학전문지 뉴잉글랜드 저널 오브 메디신(New England Journal of Medicine) 최신호에 실렸다.
빌-멜린다 재단의 빌 게이츠는 말라리아 퇴치에 "커다란 이정표"가 세워졌다면서 수많은 어린이를 말라리아에서 보호할 수 있다고 논평했다.
세계보건기구(WHO)에 따르면 2009년 약 100개국에서 78만1천명이 말라리아로 목숨을 잃었다.
말라리아에 가장 취약한 연령층인 생후 6-12주의 신생아에 대한 접종결과는 내년쯤 나올 예정이며 이 결과가 이 백신의 면역 효과를 평가하는 중요한 부분이 될 것으로 보인다.
글락소스미스클라인 사의 앤드루 위티 최고경영자(CEO)는 모든 것이 순조로우면 2015년 이 백신이 아프리카 아이들이게 배포될 수 있을 것으로 전망하면서 지금까지 백신 개발에 3억달러가 들어갔지만 백신가격은 이익을 붙이지 않고 낮은 가격에 공급할 것이라고 밝혔다.
아직 확실치 않은 것은 이 백신의 효과가 얼마 동안이나 지속하느냐는 것이다.
이 백신의 부작용은 다른 일반 백신처럼 주사한 자리가 붓고 열이 나는 정도인 것으로 밝혀졌다.
