A new double-strain polio vaccine is more effective than triple and single vaccines and means children in high-risk areas can be immunized against two key strains of the crippling virus in a single dose, scientists say.
In a study in the Lancet journal on Tuesday, World Health Organization (WHO) scientists said research on the bivalent oral polio vaccine, known as bOPV, found it induced a "significantly higher immune response" than triple vaccines.
Researcher Roland Sutter said the findings showed that the new oral vaccine, which is made for WHO vaccination programs by various drug firms including Britain's GlaxoSmithKline and India's Panacea Biotec, would be a potent weapon in the battle to eradicate the crippling virus.
"The main advantage of the bivalent is that it is so effective against type 1 and type 3 poliovirus at the same time," he told Reuters in a telephone interview.
"The impact has been quite dramatic already in India and in Nigeria with cases coming down to very low levels this year."
Also on Tuesday, the WHO announced a mass polio vaccination in Africa, the same day Ugandan health officials announced a setback in its eradication attempts.
Ugandan Health Minister Stephen Malinga says a 2-year-old boy was first diagnosed last week and four other children from his neighbourhood tested positive. Mr. Malinga says Uganda had been polio-free since 2009.
The WHO's $42.6-million (U.S.), donor-financed campaign will start soon and aims to reach 72 million children in 15 countries.
WHO cited recent outbreaks in Angola, Congo, Liberia and Mali.
Polio, which spreads in areas with poor sanitation, attacks the nervous system and can cause irreversible paralysis within hours of infection. Children under five are the most vulnerable.
In 1988, when the WHO and its partners formed the Global Polio Eradication Initiative to lead a drive to eradicate polio, the virus was endemic in 125 countries and paralyzed nearly 1,000 children every day.
Mass vaccination with older triple, or trivalent, oral polio vaccines have helped reduced the number of countries where polio is endemic to just four. But despite the use of these triple vaccines as well as monovalent, or single strain vaccines, polio virus types 1 and 3 are still circulating in the polio-endemic countries of Afghanistan, Pakistan, India, and Nigeria.
In their study, conducted between August and December 2008, Sutter and colleagues analyzed data from 830 newborn babies from three centres in India who received either the monovalent, bivalent or trivalent vaccines in two doses, one at birth and one 30 days later.
Blood samples were taken before vaccination and after the first and second doses to measure rises in antibody levels and the researchers found that, in targeting polio types 1 and 3, bOPV was better than both the triple and single vaccines.
In a commentary in the Lancet, Nigel Crawford and Jim Buttery from the Murdoch Children's Research Institute in Melbourne, Australia, said the potential effectiveness of the bivalent vaccine was already being shown in India where it is being used on a large scale. Latest polo data show just 32 cases so far this year, compared with 260 in 2009, they wrote.
But they said the global financial crisis had left a big funding gap for immunization programs worldwide which needed to be closed if the aim of eradicating polio was to be reached.
"The plan of action for polio eradication - with bOPV as the centrepiece - is only 50 per cent funded for 2010-12," they wrote. They described the potential of the new bivalent vaccine as "an important step forward" but said "a final concerted effort, both locally and worldwide, is required" to succeed in finally eradicating the virus.
With files from AP