BAGAMOYO, Tanzania (Reuters) - Billionaire Bill Gates and thousands of babies are helping Africa prepare its largest medical experiment ever, in the search for a new vaccine against malaria.

Faith Ndaa, a malaria patient, lies on her bed at the high dependency unit of Kilifi district hospital, November 26, 2008. REUTERS/Joseph Okanga

Researchers say the push comes at a crucial time in the battle against a disease which has been beaten back several times before, only to resurge with deadly vigor.

For Dr. Zena Mtajuka, an exhausted warrior on the frontlines of the fight against one of the planet’s most devastating diseases, a vaccine cannot come quickly enough.

“Malaria is our number one killer in this district,” said Mtajuka in her cramped office at Bagamoyo District Hospital north of Tanzania’s capital Dar es Salaam.

“The hardest thing is that members of the community come to the hospital too late. It makes them harder to save.”

Bagamoyo is one of almost a dozen research sites where scientists are in the final stages of preparing for a large-scale efficacy and safety trial of the “RTS,S” vaccine developed by GlaxoSmithKline PLC.

The trial, which is slated to begin in early 2009 and will involve 16,000 children in seven African countries, is the largest ever undertaken on the continent. Its funders, including groups supported by the Gates Foundation, hope it will result in a new and effective strategy against the disease.

Bagamoyo’s malaria burden is typical of many places in tropical Africa, home to most of the roughly one million people who die each year because of the mosquito-borne illness.

Public health officials estimate malaria costs Africa $12 billion due to deaths and lost productivity, a twin burden the world’s poorest continent cannot afford.

Public health advocates have cited malaria as an emerging global health success story, with new drugs, bed nets and insecticides contributing to sharp drops in infection rates in a number of countries.

Mtajuka said insecticide-treated bed nets and indoor spraying are not universally available here despite campaigns to promote them.

“Some people are using bed nets, but not all of them. Some are simply too poor to afford them,” Mtajuka said. “And since I’ve been here there’s been no indoor spraying. I think we had it once, three years ago, but not since then.”

Mtajuka, who already manages the hospital’s HIV/AIDS clinic, had to learn the malaria job fast. Her predecessor as malaria officer died earlier this year -- of malaria.

Slideshow ( 2 images )

MEASURING SUCCESS

Like many African doctors, Mtajuka remains swamped by malaria cases -- which proponents say underscores the need for a vaccine to stop the deadly parasite in its tracks.

“Drugs and nets are going to assist, but I don’t think that’s a long-term solution,” said Dr. Norbert Peshu, director of the KEMRI Center for Geographic Medicine Research in Kilifi, Kenya, another malaria hotspot.

“The final thing against malaria has to be a vaccine.”

Although identified as promising two decades ago, the RTS,S vaccine has only in recent years moved into widespread testing, thanks to funding from the PATH Malaria Vaccine Initiative supported by the Bill and Melinda Gates Foundation.

For vaccinologists, malaria has proved hard to beat. The parasite that causes the disease has a complex life-cycle inside mosquitoes and the human body, which helps it evade the immune system.

RTS,S, named for the antigen it produces, fuses part of a protein from the parasite to the surface of a hepatitis-B viral particle, stimulating the body’s immune response. This hobbles the parasite’s ability to infect and develop in the liver, its main repository in humans, which gives partial protection against the disease.

The vaccine’s largest test so far, in more than 2,000 children in Mozambique starting in 2003, showed it reduced all cases of clinical malaria by 35 percent and the worst cases of the disease by almost 50 percent.

The Malaria Vaccine Initiative, which helps coordinate world malaria vaccine research and development, aims for a vaccine that is at least 50 percent effective by 2015 and a second-generation product to confer 80 percent or more protection against clinical disease by 2025.

“It may not cover all the bases, but it could cover some of them,” said Dr. Patricia Njuguna, a Kenyan pediatrician who will be one of the principal investigators for the next series of RTS,S human trials.

“Traditional vaccines give 80 to 90 percent protection. Malaria vaccines give less. But perhaps that is all you need.”

NO SINGLE ANSWER

Many medical workers in Africa say that while even a partially effective malaria vaccine would be welcome, it would certainly not be the answer to the continent’s health problems.

Stephen Chakaya, a 27-year old medical officer at a rural clinic in Junju outside Kilifi, Kenya, said poverty and hunger were just as destructive as malaria in the community and much harder to address.

“Most of the people around here live on less than $1 per day,” Chakaya noted, standing in his basic clinic that serves nearly 6,000 people in the area.

“We don’t have a lab here. We don’t have a microscope. We don’t have slides, so we can never be sure if a case is malaria or something else. We need investment,” he said.

But researchers say the vaccine push is bringing this investment, helping to supply equipment and expertise that will eventually benefit the community at large.

In Bagamoyo, where the vaccine trials are being run by Tanzania’s Ifakara Health Institute along with the district hospital, vaccine money has helped to purchase new ambulances and equip a bright new pediatric ward that now takes care of all cases of children under 5 admitted to the hospital.

Major investment in bed nets and combination therapies with artimisinin-based drugs have added pressure on the parasite, which already appeared to be on the retreat in at least some areas of Africa.

Wendy O’Meara, a U.S. epidemiologist working at the KEMRI/Wellcome Center in Kilifi, said reviews of local hospital data showed the mean age of children admitted with malaria had been rising over the past 10 years, a signal that the parasite was becoming rarer.

She said the changes came before bed nets and combination drug therapies were widely available in Kilifi, indicating other factors were responsible.

“There are very few places on the planet where malaria runs its natural course,” she said. “It could be economic development, it could be things we don’t have data on, or aren’t creative enough to think of yet.”