How does the polio virus spread and why multiple vaccination campaigns are needed?

As government of Pakistan has resumed polio vaccination activities on July 20 with a campaign in selected districts after a four-month suspension of all polio vaccination activities due to COVID-19 pandemic, the need for awareness is more than ever.

Here are answers to some of the most pertinent questions about the disease and the vaccination campaign.

How does polio spread?

Polio is caused by a human enterovirus called the poliovirus. The virus is most often spread by the fecal-oral route. Poliovirus enters through the mouth and multiplies in the intestine.

Infected individuals shed poliovirus into the environment for several weeks, where it can spread rapidly through a community, especially in areas of poor sanitation.

Poliomyelitis can affect any age, but primarily involves children ages less than 5 years and can cause paralysis or even death.

Building immunity against virus is a very complex biological process. We are all different; as are organisms’ reactions to medications and vaccines.

Few children may acquire strong immunity after just five or six doses of the polio vaccine, while the most vulnerable children need more than ten.

The immune system of underweight, malnourished and children suffering from diarrhoea responds to the polio vaccine in a different way that of healthy children.
Therefore, to remain protected, all children under five years of age should receive polio vaccine during every immunization round.

Why multiple vaccination campaigns are needed?

To stop polio transmission, no less than 95% of all children under 5 years of age across Pakistan should be immunized during each campaign.

To achieve this high coverage is very challenging logistically. In other words, the remaining 5% that make almost 2 million unimmunized children should be reached during consecutive campaigns in a short interval to ensure all children are covered.

Furthermore, once the polio virus is detected in a certain area, an additional campaign will be carried out for that district to prevent potential outbreak of polio amongst children in the community. That is why multiple polio campaigns are done every year.

No child should miss a single dose of polio vaccine! Each additional dose is an additional protection against polio.