More than 150 countries have begun switching to a different polio vaccine, an important milestone towards polio eradication. Health campaigners say, the new vaccine will target the two remaining strains of the virus under a switchover 18 months in the planning.
Stephen Cochi, from the US-based Centers for Disease Control said the current vaccine contains live weakened virus relating to three types of polio. Thousands of people will monitor the changeover in 155 countries during the next fortnight.