Protecting against polio
Mains Paper 2: Health
Prelims level: VDPV
Mains level: Services relating to Health
The wild polio virus strains reduced by 99.9% since
The world is inching towards eradicating polio. But
unfortunately, more children today are affected by the live, weakened virus
contained in the oral polio vaccine (OPV) that is meant to protect them.
The weakened virus in the vaccine can circulate in the
environment, occasionally turn neurovirulent and cause vaccine-derived
poliovirus (VDPV) in unprotected children.
While the wild-type virus has caused 22 and 25 polio cases
in 2017 and 2018 respectively, in just two countries (Pakistan and Afghanistan).
VDPV was responsible for 96 and 75 polio cases in more
countries during the same periods.
“Paradoxically, vaccination (using OPV) has become the
main source of polio paralysis in the world,” notes a 2018 paper in The Lancet.
The VAPP burden
The circulating VDPV strains are tracked, and
outbreaks and cases are recorded and shared, little is known about
vaccine-associated paralytic poliomyelitis (VAPP) cases, particularly in
VAPP occurs when the virus turns virulent within the body
of a recently vaccinated child and causes polio.
The frequency of VAPP cases varies across countries.
With high-income countries switching to the inactivated
polio vaccine (IPV) that uses dead virus to immunise children.
The VAPP burden is concentrated in low-income countries
which continue to use the OPV.
The WHO had suggested a rate of 1 case of VAPP per million
births and had estimated the annual global burden of VAPP to be approximately
120 cases in 2002.
Under these circumstances, India’s share would been merely
25 VAPP cases per year, based on the annual birth cohort of 25 million.
The observed number of cases in India in 1999 was 181.
This indicates that the actual risk is seven times the
It is reasonable to assume that there would be 400-800
annual cases of VAPP globally,”
That would have meant that there were 100-200 VAPP cases
in India each year.
The global estimated incidence of VAPP was then revised to
Switching to IPV
The reason for not switching over to the IPV is
because global production was too low to meet India’s demand.
India is the largest cohort. It needs 48 million doses per
year to immunise all children.
The IPV is essential for post wild-type polio virus
eradication, to get rid of VDPV and VAPP.
The globally synchronised switch from trivalent to
bivalent OPV in mid-2016 was accompanied by administering a single dose of the
IPV prior to administering the OPV.
A single dose of the IPV given before the OPV prevents
A single dose of the IPV primes the immune system and the
antibodies against the polio virus, seen in more than 90% of immunised infants.
With no way of monitoring VAPP cases in India, there is no
way of knowing if the use of a single dose of IPV followed by immunisation using
bivalent OPV has led to a reduction in the number of VAPP cases.
Despite knowing that there is a higher burden of polio
caused by oral vaccines, India continued to use the OPV.
The decision to use only the OPV was faulty. Parents were
obliged to accept the OPV and face the consequences of VAPP as well as VDVP.
It is easier to administer the OPV than the IPV and the
cost per dose of OPV is also lower than that of the IPV.
However, the OPV fared poorly on two important counts:
safety and efficacy.
Administering the OPV was easier than the IPV but no
cost-benefit analysis was done before choosing the OPV.
Three doses protected only two-thirds of Indian children
and many developed polio before they turned one year. So we had to give more
doses per child.
The high-income countries preferred the IPV, India and
other low-income countries continued to rely on the OPV.
India licensed the IPV only in 2006 but did not introduce
it in routine immunisation.
Q.1) Consider the following statements regarding the Universal Immunisation
1. It aims to protect children from noncommunicable diseases.
2. It covers both children and pregnant mothers.
3. It is funded by the centre and states on 50:50 basis.
Which of the statements given above is/are correct?
(a) 1 and 3 only
(b) 1, 2 and 3
(c) 2 only
Q.1) Why the inactivated polio vaccine is essential for India?
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