Polio vaccine: which is the best

India has reported only one polio case this year making it the longest polio-free period ever since eradication efforts were launched. The only case of polio reported this year has been from Howrah district in West Bengal on January 13 compared to 39 cases in the country in the same period of 2010. Now let us know what exactly polio is:

Polio is a disease caused by a virus. It enters a child's (or adult's) body through the mouth. Sometimes it does not cause serious illness. But sometimes it causes paralysis (can't move arm or leg). It can kill people who get it, usually by paralyzing the muscles that help them breathe. Polio used to be very common in the United States. It paralyzed and killed thousands of people a year before we had a vaccine for it.

History: A 1916 polio epidemic in the United States killed 6,000 people and paralyzed 27,000 more. In the early 1950's there were more than 20,000 cases of polio each year. Polio vaccination was begun in 1955. By 1960 the number of cases had dropped to about 3,000, and by 1979 there were only about 10. The success of polio vaccination in the U.S. and other countries sparked a world-wide effort to eliminate polio.

Today: No wild polio has been reported in the United States for over 20 years. But the disease is still common in some parts of the world. It would only take one case of polio from another country to bring the disease back if we were not protected by vaccine. If the effort to eliminate the disease from the world is successful, some day we won't need polio vaccine. Until then, we need to keep getting our children vaccinated.

But now the question arises which is the best vaccine, the bivalent oral vaccine (BOPV) or the injectible one (IPV). To see which one boosts mucosal immunity (also known as gut immunity) now both are being tested and also for their protection levels. Though IPV is not used in India right now, we must know its protection capability for the future and compare it with what we are presently using.

In the study, 990 healthy children in three age groups - six to eleven months, five years and 10 years - have been divided into three groups - one that receives an additional dose of BOPV, an additional dose of IPV and one which does not get any vaccine. Experts say that the children participating in the study will benefit by the additional polio vaccines which will help boost their immunity against the crippling disease.

The study findings will also help to assess the best options for immunizing children in the post-polio eradication phase.