By Nina Larson
A World Health Organisation expert panel is calling for a shift in the kinds of vaccines used to fight polio, insisting full eradication of the crippling disease is within reach.
The WHO Strategic Advisory Group of Experts (SAGE), which advises the UN health agency on immunisation policies, warned that among the biggest obstacles to eradicating polio were the sporadic outbreaks of the disease caused by the live polio virus used in some vaccines.
"We think it's realistic that we will get polio eradicated in the next few years," SAGE chairman Jon Abramson told reporters in Geneva.
After facing hundreds of thousands of cases of polio as late as the 1980s, there have so far this year been just 51 people infected with the wild form of the crippling disease that affects mainly young children.
With no cases of wild polio registered in Africa since August 2014, the wild version of the virus now exists only in Afghanistan and Pakistan.
"The problem now is that we are seeing more cases of vaccine-caused polio than we are of wild type," Abramson said.
Vaccine-derived polio infections are in rare cases caused by one type of polio vaccine, which contains small amounts of the weakened but live polio virus.
Oral polio vaccine (OPV) replicates in the gut and can be passed to others through faecal-contaminated water, thus imperilling unvaccinated children.
Abramson said it was "a rare event to see vaccine-related paralysis," but pointed out that "when you're giving millions and millions and millions and millions of doses, you do see it".
WHO has already recommended that OPV be phased out worldwide and replaced by the inactivated polio vaccine (IPV), but the shift is taking time because of supply shortages.
Abramson says there are two types of OPV - one that protects against all three types of the crippling disease and one that protects only against types one and three.
Since the so-called trivalent vaccine containing the type two polio virus causes the most outbreaks, SAGE is now calling on countries still using this vaccine to replace it with the bivalent version by May next year.