The vaccine swap has been described as the largest vaccine roll out in history to end Polio
The World Health Organisation (WHO) has launched a new vaccine to eradicate the last two strains of the polio left in 155 countires.
The Bivalent Oral Polio vaccine which protects against two strains type 1 and type 3 wild virus replaces the Trivalent Oral Polio vaccine which protects against all three.
Type 2 Polio was eradicated in 1999 which means immunizing against it now is pointless.
In the next few weeks the 155 countries will be engaged to ensure a successful switch.
Only 12 cases of type 2 were reported worldwide in Pakistan and Afghanistan. WHO predicts that this strain will be totally wiped out in a decade.