Between 17 April and 1 May, the world is marking a historic milestone with 155 countries and territories switching from trivalent to bivalent oral polio vaccine in a globally synchronized manner.

Be a part of the action and track countries as they undergo the switch, find out why it is so important and how 155 countries and territories are making it happen.

Read more about why the switch brings the world one big step closer to eradicating polio here.