Polio, or poliomyelitis, is a highly infectious disease caused by a virus. It invades the nervous system and can cause total paralysis in a matter of hours especially in children under the age of five.
Today, more than 150 countries have begun the switch to a different polio vaccine which health campaigners say, marks an important milestone towards polio eradication.
The new vaccine will target the two remaining strains of the virus under a switchover 18 months in the planning which includes dealing with a global stockpile of 100 million doses of vaccine targeting just type 2, built up as an insurance policy in case of any outbreak.
To disabuse the fears of many who believe previous supply of the vaccine will be destroyed, the World Health Organization has denied some media reports that “millions” of doses of the old vaccine would need to be destroyed, by incineration or other approved means. Furthermore, WHO director of polio eradication, Michel Zaffran, says, “Some will need to be destroyed – but this will be a few vials, not trucks full of vaccine.”
This is because a weakened version of the of type 2 polio virus will be excluded from the new improved polio vaccine which was eradicated in 1999.
Dr Stephen Cochi, from the US-based Centers for Disease Control (CDC), says, “The current vaccine contains live weakened virus relating to three types of polio. But we don’t need the type 2 component, as it’s not in the world any longer and in very rare cases, it can mutate and lead to polio, through what’s called ‘circulating vaccine-derived’ virus.”
“So removing type 2 from the vaccine takes away that risk – and ensures we have a vaccine which will work better dose by dose.”
Thousands of people will monitor the changeover in 155 countries during the next fortnight and it is taking effect mainly in developing countries, but also in richer ones such as Russia and Mexico.
The new vaccine will still be given as drops in the mouth, so healthcare workers will not need fresh training.
Switching the vaccine from one successfully used to fight polio for more than 30 years is a huge logistical exercise in sustaining health. Indicators show that there were just 74 cases of the paralysing disease in 2015 and there have been 10 so far, this year.
Africa has been free of polio for more than a year.