An overview of Polio Vaccines OPV & IPV

India along with 10 other countries was certified as “polio free” nation on the 27th March of 2014. It has been five years since the last confirmed case of polio in our country. A simple sentence for a foreigner, but a huge achievement as far as India is concerned.

Till 2014 India has used the trivalent oral polio vaccine (tOPV) in the routine national immunization programme. The same vaccine is being used for the pulse polio programme which I’m sure all of us are very familiar with.

We have continued the use of OPV even after the historic day in 2014 and now India is ready to introduce another (injectable) vaccine to prevent polio. But why? What is the need for another vaccine?

In order to understand the answer for that question one should be familiar with the two types of vaccines to prevent polio. This article will tell you all the stuff that you need to know about polio vaccines.

The two Polio Vaccines : OPV & IPV

Parents all around the world love the oral polio vaccine (OPV) simply because of the route of administration of that vaccine. There is no need to prick their child with a needle to deliver the protection offered by the OPV. Two drops of vaccine are put on the baby’s tongue and that’s it.

As some of you must have already heard, there is a second type of vaccine to prevent polio. It’s called the inactivated polio vaccine (IPV) and it’s given as an injection and not orally. Let us now learn the basic difference between IPV and OPV.

OPV vs IPV : Polio Vaccines

When used correctly, both OPV and IPV are safe and effective. It is essential to vaccinate every newborn child by 6 months of age. This is because the polio virus infects children in the age group of 6 months to 3 years.

Now that you know the two types of polio vaccines, which one would you prefer?

Well, as far as you live in India, you need to give both the vaccines to your child for full proof protection from the paralysing disease. Wondering why?

MUST READ : How to Make sure that the Vaccines are Potent?

India is now “polio free”, do we still need Vaccines?

One must understand that the transmission of polio virus is still taking place in many parts of the world. Not all countries in the world have been declared as “polio free”.

India is particularly at high risk of re-infection with the polio virus. This is because of it’s close proximity with Pakistan and Afghanistan where polio cases are still at large. India was declared a polio free nation only very recently. Before that time, there would have been free transmission of polio virus from India to other parts of the world. This is true considering the large number of Indian citizens working in other countries. Therefore, chances of re-infection through the same route is possible. Programmes like routine and pulse polio immunization have to be continued until this deadly incurable disease is eradicated globally.

This can be achieved only with the proper use of polio vaccines. While OPV helps prevent paralysis and reinfection of the entire population, IPV offers better personal protection.

IPV is an important tool in the “endgame” strategy for the eradication of polio from this world. Many countries have already introduced IPV in their national immunization programmes. India is complying to the global target of polio eradication by introducing IPV in 2016.

As long as Pakistan and Afghanistan becomes polio free countries, India will have to continue the use of both OPV and IPV. With the double protection, India can continue to be Polio free and help in the global cause of polio eradication.

India was certified polio-free on 27 March 2014, but the immunization programme continues in the country since two of its neighbours stay polio-endemic and due to the threat of vaccine derived polio virus (VDPV).

Inactivated Polio Vaccine (IPV)

Also known as the Salk Polio Vaccine. The letter “I” in IPV stands for “inactivated” and not “injectable”. As far as the Indian population is concerned, IPV is a new vaccine. But, this is true only in the government-run public hospitals. The private hospitals in India have been giving IPV vaccines for many years now.

As the name denotes, IPV has inactivated polio virus particles. The virus proteins retain their antigenicity but are actually killed. That means, there is zero percent chance of infection after vaccination, or commonly refered to as vaccine associated paralytic poliomyelitis (VAPP). This is unlike the OPV which contains live and attenuated virus proteins. To mitigate the risk of VDPV emergence, introduction of at least one dose of IPV was recommended by SAGE in 2012.

Vaccine Associated Paralytic Poliomyelitis (VAPP)

Oral polio vaccine is a safe and effective vaccine. But, on rare occasions adverse events may occur. Vaccine associated paralytic poliomyelitis is the most important of these rare adverse events. Wild polio virus (WPV) are the most important agent causing polio. The type -2 strains of polio viruses used in the preparation of OPV can rarely result in paralysis. This is called VAPP. The cases of VAPP are clinically similar to those caused by wild polio virus. In countries using OPV, the incidence of VAPP is estimated at around 4 cases per one million birth cohort.

VAPP occurs in both OPV recipients as well as in unimmunized children. VAPP is caused by vaccine derived polio viruses. Because of the risk of emergence of VDPV, the use of OPV will be discontinued worldwide once all the wild polio virus transmission has been interrupted.

Now, as explained earlier the IPV doesn’t have any risk of causing VAPP (IPV uses killed and inactivated virus particles). This makes IPV  safer than OPV. Thus with time, IPV will replace OPV.

Why are we still using OPV then?

To answer this question, one should know the global guidelines for polio eradication. Even though OPV has adverse effects like VAPP, it is still the most effective vaccine that can prevent polio. The live attenuated virus particles provides immunity by entering our body through the gut ; acting in a way the wild polio virus does. It protects the recipient child, as well as the unimmunized children living in the neighbourhood of the vaccinated child. For a country like India, this is something of utmost importance considering the resistance against vaccination and the financial constraints.

The Global Polio Endgame Strategy

Polio Eradication Endgame Strategic Plan, 2013-18 (PEESP) provides global guidance for implementation of this strategy and was endorsed in May 2015 during World Health Assembly. That Assembly was represented by Ministers of Health of all 194 Member States including India.

India is committed for the implementation of global polio endgame strategy that addresses the eradication of all polio disease, whether caused by WPV or VDPV to achieve a world free from polio.

The strategy involves :-

1. Switch from trivalent Oral Polio Vaccine (tOPV) to bivalent Oral Polio Vaccine (bOPV).
2. Introduction of at least one dose of IPV before the “switch”

The Switch from tOPV to bOPV

This switch is associated with risk of time limited type 2 VDPV outbreaks because of silent transmission resulting from replication and mutation of type 2 vaccine virus in gut of recently immunized children. The risk of VDPV outbreak is related to low population immunity against particular serotype. Strategic Advisory Group of Experts on Immunization (SAGE) to World Health Organization in its October, 2015 meeting affirmed a two weeks global tOPV to bOPV switch window of 17th April 2016 to 1st May 2016. Accordingly, our country has decided National Switch Date as 25th April, 2016.

The switch is being carried out in the following steps :

• Taking back all the tOPV from all healthcare institutions in India starting from the grassroots (sub-centre level).  Not even a single vial of trivalent OPV should be stored in any healthcare institution in the country. This is applicable for even the private hospitals.
• Supplying the new bivalent OPV after confirming that the trivalent OPV have been taken back.
• Making bivalent OPV part of the routine immunization programmes and pulse polio programmes from April 25 onwards.

After April 25 of 2016, you will not find a single vial of trivalent OPV in India.

NOTE : The switch is being done only for the OPV. The IPV is also trivalent (but killed and inactivated) and no switch is required in this vaccine.

Global Status of IPV introduction:

As part of the PEESP recommendations, all 126 countries which, at the start of 2013 were only using OPV, were required to introduce at least 1 dose of the IPV into their routine national immunization programme schedule as part of preparations for the switch. The level of commitment from all countries to meet this timeline has been exceptional and as of February 2016, 91 of the 126 countries have introduced IPV in their routine immunization schedule.

IPV in India

There would have been many who had doubted India’s ability to achieve the “polio free” certification. But it has happened. Now, the big challenge is to continue the routine OPV immunization and to introduce the IPV in the national immunization programme. There are a few differences in how the IPV is going to be introduced in India compared to the other countries in the world. This is mainly due to the vaccine shortage. The recommended route of administration of IPV is either intramuscular or subcutaneous.

IPV because of it’s shortage will be introduced in two phases. The first phase was started in November, 2015 when the vaccine was given in 6 high risk states of India including Assam, Gujarat, Madhya Pradesh, Uttar Pradesh, Punjab and Bihar. In these states the vaccine was given to babies who were just 6 weeks old along with the third dose of OPV.

Before the “switch” of tOPV to bOPV, it is planned to initiate the second phase of IPV in 22 states and union territories. In these states, IPV will be given as 0.1 ml intradermal injections instead of 0.5 ml intramuscular shots. This decision was taken by the government of India in late February 2016. The intradermal injections will be given at 6 weeks and 14 weeks after birth as two fractional doses. Studies have shown that such an administration is as effective as a single intramuscular injection.

IPV introduction is going to be a tough task for the Indian healthcare workers. It is a big step in the right direction.

IPV might be a new vaccine as far as India is concerned. Actually speaking, the IPV was first used in the year 1955. More than thirty countries have included IPV in their national immunization programme. India along with about 125 other countries are on the verge of doing the same.

“IPV is a key step towards global endgame strategy. It is a tough task to convince a population to continue with OPV after a country is declared polio-free and even harder to introduce IPV on top of that,” said Louis George Arsenault, country representative India, UNICEF.

Now, the question is – “Can India do it?”

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