India's fight against polio
What is the status of polio in India ?
- No existing cases of polio in India.
- India became polio free in 2014.
Why is India carrying out Pulse Polio Campaigns inspite of being polio free ?
Polio can re-emerge at any point of time and the only way to keep it out is make sure that all the vulenrable population is immunised against it.
There are two ways in which India can be exposed to recurrence of polio :
- Polio virus can spread into India from across the borders though Afghanistan and Pakistan.
- The second risk of resurgence comes, ironically, from OPV (Oral Polio Vaccine) itself.
How does polio spread from OPV ?
- In rare cases, Oral Polio Vaccine, which contains weakened but live polio virus, can cause paralytic polio.
- Also, because the vaccine virus is excreted by immunised children, it can move from one person to another.
- Vaccine derived poliovirus (VDPV) is mutant of the polio virus which sticks around after OPV is administered in certain cases . VDPV, like imported wild polio, can cause outbreaks in underimmunised population
What is the alternative to OPV ?
- Inactivated Polio Vaccine (IPV), IPV does not cause VDPV but protects children equally well against polio.
Way forward for India :
- Out of the three wildtypes of poliovirus that cause the disease, the transmission of one, Wild Poliovirus 2 (WPV2), was interrupted successfully more than a decade ago.
- The two remaining viruses that are circulating in Pakistan and Afghanistan are WPV1 and WPV3.
- Once we stop these two viruses in their tracks, OPV will be phased out and replaced globally with IPV.