India has not reported a single case of polio caused by the wild polio virus (WPV) since January 2012. Hence, India was declared polio free in 2014 by the World Health Organization. But, it should be noted here that India is free only from wild polio virus (WPV). Cases of non-polio acute flaccid paralysis (AFP) are still being reportedfrom different states across the country.
- Between January 2014 and March 2015, India reported four cases from four different States, of vaccine-derived polio.
- Different data show that there has been a surge of non-polio AFP since India eradicated polio. The number of cases reported in 2012 was 59,436, in 2013 it was 53,421, and in 2014 it was 53,383.
- Three years after India reported its last case of WPV, the country has, in one form or another, been reporting around 50,000 cases of flaccid paralysis that, clinically, is exactly like polio, indicating how hollow the polio-free status is.
What is flaccid paralysis?
The polio virus causes paralysis — medically known as an acute flaccid paralysis (AFP). It is characterized by sudden muscle weakness, and fever in one or more limbs. Clinically, it is exactly like polio.
- AFP can occur due to many reasons, one of which is vaccine-linked. AFP can also arise for other reasons, including infection by non-polio pathogens.
Experts say that there is an undeniable link between the increase in incidence of NPAFP (non-polio AFP) and the number of OPV doses delivered in any region. How?
- Oral polio vaccine (OPV) contains an attenuated (weakened) vaccine-virus. The weak form of the polio virus is used to activate an immune response in the body, which then protects the child when challenged by wild polio virus (WPV).
- But when a child is immunised with OPV, the weakened vaccine-virus replicates in the intestine. During this time, the vaccine-virus is also excreted. In areas of inadequate sanitation, this excreted vaccine-virus can quickly spread in the community and infect children with low immunity.
- This excreted vaccine undergoes genetic changes as it circulates in the community and causes Vaccine-derived polioviruses (VDPV).
The cases of VDPV are rare as it has to circulate for a long time in the community of under-immunised populations before it can infect and cause paralysis in someone.
Where the real problem lies?
- The problem is not with the polio vaccine itself, but low vaccination coverage. Vaccine-derived polioviruses (VDPV) is circulating in the community that is under-immunised.
- This marks the failure of the Central government — which even in best case scenarios has achieved only 70% immunisation coverage, leaving a massive group susceptible to poliovirus, vaccine derived or otherwise.
How to tackle this problem?
- As per the WHO norms, the best way to cope with cases of non-polio acute flaccid paralysis (NPAFP) and Vaccine-derived polioviruses (VDPV) is a synchronised switch from trivalent to bivalent Oral polio vaccine, which India has already done.
- To further prevent the risk of re-emergence, a booster dose of inactivated polio vaccine (IPV) is recommended in routine immunisation, prior to the switch.
At present, the government’s only strategy to combat the invisible kinds of polio is the addition of inactivated polio vaccine (IPV).
Who is more vulnerable?
A 2005 study in the Indian Journal of Medical Research on NPAFP found that a fifth of cases of NPAFP were reported from Uttar Pradesh. On follow-up after 60 days, researchers realised that 35.2% children had residual paralysis and 8.5% had died making the total of residual paralysis or death a startling 43.7 %. This shows that children who had NPAFP are more than twice at risk of dying than those who get infected with wild polio virus (WPV).
Most of the country’s non-polio AFP cases occur in just two States — Bihar and Uttar Pradesh. They accounted for about 61% of the 53,000-odd non-polio AFP cases identified in the country in 2012. As a result, the two States have far higher annualised non-polio AFP rates than other States — around 34 for Bihar and about 23 for Uttar Pradesh. The rate for the country as a whole is slightly over 12.
India may be polio-free but the world’s largest number of NPAFP cases are being reported here. Introduction of an Injectable Polio Vaccine (IPV) in its routine immunisation programme is a good step in the right direction. But, the country needs an urgent policy intervention to address NPAFP and VDPV with the same urgency and political will with which the country addressed the wild polio virus cases.