Concerns about whether countries can effectively deliver a moderately protective four-dose malaria vaccine have prompted advisers to the World Health Organization to hold off recommending its broad use.
Instead, two advisory groups called Friday for large pilot studies to test if and how the world's first malaria vaccine can be incorporated into childhood vaccine schedules in countries with moderate to high malaria transmission rates.
Those studies could take three to five years to conduct and involve as many as one million children, said Dr. Jon Abramson, a pediatrics professor at Wake Forest University School of Medicine in Winston-Salem, NC.
Abramson is chair of a group called the SAGE — the Strategic Advisory Group of Experts on Immunization. It made the malaria vaccine recommendation jointly with the WHO's Malaria Policy Advisory Committee.
The malaria vaccine — known as RTS,S — is the first to successfully target a parasite. It is made by British pharmaceutical giant GlaxoSmithKline Plc (GSK).
Studies have shown the vaccine is about 39 percent effective at reducing malaria infections. While it doesn't perform as well as many other vaccines, malaria causes such a high burden of disease and death that even a modestly protective product could save many lives.
But the vaccine must be given at ages that put it out of sync with the normal schedule of childhood vaccinations, which can be a significant problem in rural Africa. Giving a number of vaccines at the same time limits the drain on health care resources and increases the chances that children get all their shots.
The first three doses of the vaccine are given between the ages of five and 17 months. The fourth is given 15 to 18 months after the third dose.
The fourth dose is of particular concern, Abramson said. No other childhood vaccine is given at that time, which may make parents less likely to return with the child to get it. Without it, the benefit from the earlier doses is quickly eroded, he said.
The demonstration studies will determine if parents can be enticed to ensure their children get the fourth dose.
"If we can't get four doses of this vaccine into the children, we're not going to be using it in the long run," Abramson said. "We think we can, but it's going to be a lot of hard work and it's going to be a lot of effort to figure out how we can do it."
Abramson said the pilot studies will also give the WHO a better sense of how effective the vaccine is at reducing malaria deaths among children. Modeling studies have suggested it could cut deaths by 28 percent, but mathematical models produce estimates, not evidence, he said.
The WHO must decide if it wants to accept the recommendation. But it would be rare for the agency to reject such advice, said Tracey Goodman, a WHO immunizations expert. The agency has said it will issue a position on RTS,S use by the end of this year.
The non-governmental group Doctors Without Borders called the recommendation "rational," saying it won't start offering children RTS,S through its programs.
"Most areas with a high burden of malaria cases are in low-resource settings with weak health systems, so the successful introduction of RTS,S in these areas would be extremely challenging, requiring intensive resourcing better placed on scaling up existing malaria treatment and prevention activities," the group said in a statement.
GSK and the PATH Malaria Vaccine Initiative — a program established to spur development of a malaria vaccine — said in a joint statement that they will work with the WHO to support the research.
On another vaccine matter, the SAGE recommended the Global Polio Eradication Program proceed with a long-planned move to drop one component from the standard oral polio vaccine.
The standard vaccine protects against three types of polio viruses. But Type 2 viruses were recently declared eradicated; the last case of polio caused by Type 2 viruses occurred in 1999.
It's been known for more than a decade that the Type 2 component is causing more problems than it fixes. The weakened vaccine viruses, which can spread from vaccinated children to unvaccinated ones, can regain the ability to paralyze.
The incidence is rare. But with no Type 2 polio viruses circulating there is no benefit, only risk, from including that component in the vaccine. Last year 55 children were paralyzed by Type 2 vaccine viruses while 342 were paralyzed by so-called wild polio viruses, according to figures compiled by the Global Polio Eradication Initiative.
"We need to stop using that vaccine," Goodman said.
The plan is to stage a synchronized global switch. During the last two weeks of April 2016 all countries that use oral polio vaccine will stop administering the three-component oral vaccine, adopting the two-component or bivalent oral vaccine.
The United States and most developed countries use the more expensive injectable polio vaccine, which is made from killed viruses that cannot paralyze.