India held its annual National Immunization Day for polio on February 25th. The country has now gone two full years without a single new case. If India continues on this track, it will be declared polio-free in February 2014. This marks a significant feat for India, and more so for the global health community, given that the Global Polio Eradication Initiative began in 1988 -- over 25 years ago -- as a partnership between UNICEF, Rotary International, the Centers for Disease Control, and the World Health Organization. During each National Immunization Day, approximately 170 million children under the age of five are vaccinated.

Because so many children suffer from malnourishment and dysentery, they need to be repeatedly vaccinated up to the age of five.

All children under the age of five get two drops of the oral polio vaccine (OPV). Each two-drop dose of the vaccination costs 60 cents.

Two health workers man a polio booth from 8 a.m. to 5 p.m. on National Immunization Day. They will later go door-to-door checking for children who may have been missed.

Children crowd around a vaccination booth in Aligarh, India, a city that once had a significant number of cases but has been polio-free for over two years now.

Children are given stickers and toys with "End Polio Now" written on them. By having these signs everywhere -- on walls, in street crossings, at clinics, and even on the kids themselves, they're able to make everyone aware that an immunization round is taking place.

The oral polio vaccine must be kept in a cold chain, meaning that it cannot stay out for long periods of time in warm weather. When the square on the vile changes color, that means that the vaccine is no longer okay to use.

Children's pinky fingers are marked with ink to indicate that they've received the vaccination.

The polio health workers keep meticulous records of the number of children vaccinated. They use the previous month's records to gauge whether or not they've hit the targeted number of children in a vaccination round. While on a national level, India has only two immunization days for polio, the regions that have been strongly hit by the virus, such as Uttar Pradesh and Bihar, see routine immunizations almost every month.