[ABUJA/CAIRO] Research in Egypt and Nigeria has confirmed that a new vaccine, which only acts against the most common strain of polio, is far more effective than a vaccine targeting multiple strains of the virus.
The finding could give new impetus to efforts to eradicate polio in all countries still suffering outbreaks.
The new monovalent vaccine targets the type 1 strain of polio, while the existing trivalent vaccine targets all three strains.
In Nigeria, researchers found that 67 per cent of children in the data they analysed that had been immunised with the new vaccine between 2001 and 2007 were protected against type 1 poliovirus. In comparison, only 16 per cent of children immunised with the trivalent vaccine were protected against type 1.
In the Egyptian study researchers randomly assigned 421 newborns to receive either the monovalent or trivalent vaccine. They found that those receiving the new vaccine had significantly higher levels of antibodies against type 1 polio, with 55.4 per cent in the monovalent group, and 32.1 per cent in the trivalent group producing antibodies.
The new vaccine also worked in babies that had the "false positive" of temporary antibodies derived from their mother, and reduced the risk of polio transmission through vaccine excretion in human waste, says co-author Maha Salama from the Cairo-based Eastern Mediterranean office ofthe WHO.
"The [Nigeria] study shows that even though this vaccine only targets one type of polio, it is four times as effective as the trivalent vaccine which acts against all three polio strains," says co-author Alex Gasasira of the WHO in Abuja, Nigeria.
The data used in the Nigerian research covered the country's upsurge in polio in 2003, when politically motivated disruption of the vaccine rollout in just one state for less than a year triggered polio outbreaks across the country and then internationally.
But co-author Emmanuel Abanida of Nigeria's National Primary Health Care Development Agency told SciDev.Net that polio had been declining in northwest Nigeria even before the introduction of the new vaccine in 2007.
He says greater immunisation coverage — using any vaccine — and new techniques designed to alleviate parents' fear and suspicion of vaccines, such as offering other health assessments and treatments alongside the polio drops, helped the situation.
Both studies were published last month (16 October) in the New England Journal of Medicine.
New England Journal of Medicine 359, 1655
New England Journal of Medicine 359, 1666 (2008)