POLIO VACCINE

What is polio vaccine given for?
Polio vaccine is given to protect against poliomyelitis, the dreaded childhood disease leading to paralysis of various groups of muscles. Polio is caused by 3 types of poliovirus- type I, II & III.

What are the types of polio vaccine?
There are two types of polio vaccine, one is live oral polio vaccine (OPV) & the other is injectable killed polio vaccine (IPV). Both these vaccines contain all the 3 types of polioviruses.

Which of the 2 types of polio vaccine is used?
India & many other countries use only OPV. Infact IPV is not available in India. IPV was the first polio vaccine to be marketed in the world. Western countries like USA used IPV for mass vaccination and were immediately rewarded with significant drop in polio cases. Subsequently OPV was introduced in the market. Because of convenient oral route and cost effectiveness, the whole world started using predominantly OPV. Extensive coverage with OPV in the Western Hemisphere almost eradicated poliomyelitis. Now that there are no cases of clinical polio for 10 years or more, USA has totally switched over to only IPV and does not use OPV anymore.

After polio is eradicated from a country, it may be prudent to switch over to IPV.

How are polio vaccines available?
OPV is available as vial containing multidoses. The dose is 2 drops per dose. IPV is available as a single dose vial containing 0.5 ml of vaccine. It is also available as combination vaccines containing IPV+DPT or IPV+DPT +Hepatitis B or IPV+DPT+Hib or IPV+DPT+Hepatitis B+Hib.

When is OPV given?
OPV is given as 2 drops per orally. The first dose is given at birth –15 days as zero dose OPV. Next 3 primary doses are given at 4 weeks interval starting at 6—8 weeks of age. It is given along with 3 primary doses of DPT. Indian Academy of Pediatrics recommends a 5th primary dose at 6 months.

When is the booster dose of OPV given?
A booster dose of OPV is recommended at 15—18 months of age and a 2nd booster at 4—6 years of age.

What are the side effects of polio vaccines?
OPV has minimum side effects. It can lead to GI upset like diarrhea, vomiting. It does not lead to fever. Most of the side effects seen with OPV +DPT are due to the DPT vaccine. The most important but extremely rare side effect with OPV is vaccine-associated paralysis (VAP). It occurs in 1 in million doses. Massive benefits of OPV far outweigh the rare risk of paralysis. In west, though, it can become a medico –legal problem. Hence in west, people use first IPV to induce systemic antibodies & then use OPV, which will lead to local gut immunity without the risk of vaccine induced paralysis due to the partial immunity conferred by prior IPV.

IPV can lead to local side effects like pain, swelling, redness and tiredness in 10 –20 % of vaccinees. It can lead to fever, which is mild & lasts for 24—48 hours.

What are the contraindications of polio vaccine?
OPV is contraindicated in patients with low immunity especially if IPV is available. OPV can be given to a patient with diarrhea, but that dose should not be counted & should be followed by an extra dose. IPV is contraindicated if patient has developed severe adverse effect to its use in past.

What if a child comes late for polio vaccine?
Paralytic poliomyelitis can occur till 15 years of age. Most of the children are immune by 5 years naturally due to subclinical infections. Hence, OPV is given to any child who presents till 5 years of age. Such a child should receive 3 primary doses followed by 1st booster 1 year after 3rd primary dose & a second booster 3 years –4 years after the 1st booster dose provided the child is still less than 5 years old then.

Can polio vaccine be given along with other vaccines?
Both OPV /IPV can be given along with other vaccines.

What is pulse polio immunization?
It is a strategy of mass immunization by which one can eradicate poliomyelitis. Extra doses (pulses) of OPV are given to all children below 5 years of age in an area (like country, state, city) at a time on a given day. Such pulses are repeated every year. The aim is to achieve 100% coverage.

How does pulse immunization work?
Wild poliovirus can survive either in the intestines of a susceptible host (usually children < 5 years of age) or in the sewage water. In the sewage water it can survive only for 48 – 72 hrs & hence it has to find shelter into another susceptible host for it to survive & to continue cycle of transmission. When you give pulse OPV to all the children of < 5 years of age, the intestines of these children are flooded by vaccine virus and hence wild poliovirus cannot get entry into it. As wild poliovirus cannot survive for more than 48-72 hrs in environment, its circulation will drastically fall. When such pulse is repeated after 6 weeks it still further reduces transmission. Such pulses done every year will ultimately eradicate the wild poliovirus from nature.

Do you need to give regular OPV doses when pulse OPV is taken?
The answer is an emphatic yes.

 

Last updated on 02-12-2003