The current issue


[Updated on November 6th, 2018]

Inform everyone in family as well as those who have babies. Do not give oral polio dose to the baby till next update” This and similar messages went viral on social media last month and parents were naturally concerned. Many parents forwarded these to me: they wanted to know if it is really true. Although I replied each of them that this is a baseless rumour, the persisting queries of parents even now made it clear that there are lingering doubts and a genuine news on three batches of one brand of oral polio vaccine (OPV) used in govt. sector in four districts is being grossly misinterpreted and is being made to appear as if some dangerous virus has been found in the vaccine. In contrast, the fact is that the vaccine continues to be a life-and-limb saving concoction and the risk of skipping the doses of these “do boond zindagi ke”( “two drops of life” ) can be huge. Numerous examples round the world from Israel to Venezuela to Papua New Guinea have shown that any drop in routine vaccination against polio helps the dreaded virus to raise its head even years after elimination from the region.

The FAQs answered in simple, layman’s language with minimum medical jargon with an aim to empower parents with some basic knowledge on how vaccines work and what the whole controversy is all about.


Q. 1. Is the news of “contamination” of some batches of OPV genuine? Is the matter so serious that the director of the concerned pharmaceutical industry has been arrested?

A. Yes, the news is genuine. It is also true that the matter is serious…but it is to be clearly understood that the “seriousness” of the issue is related to the National Polio Eradication Program and even the “contaminated” OPV has not raised any safety issue for the babies who have received these doses inadvertently. To understand it, one needs to know about how our immune system work, how vaccines work and also about our National Polio Eradication Program. Upcoming questions would take these issues in detail and then come back to this again. There is absolutely no reason to panic as parents and all doses of Polio vaccines, including the Pulse Polio rounds (“Polio Ravivar”) need to be continued as scheduled. In fact, the risk is increased if one skips the scheduled doses. Remember, it is a life-and-limb saving vaccine.


Q. 2. How does our immune system work?

A. Our immune system is very complex and there are several layers of defense to avoid entry and / or destroy the bacteria/ viruses/ other invaders that gain entry in our body. However, I would explain in brief only the part of immune system that produces antibodies and kills the invading microbes, as this is related to vaccines. When any microbe (virus/ bacteria) invades out body, our immune system automatically triggers a complex chain of events and starts preparing to defeat the invader. One of the processes is production of specific antibodies that are designed specifically to kill the particular invader. Antibodies are like bullets that can hit and kill the invader. But unlike the “bullet”, they are designed to hit only the targeted bacteria/ virus and nothing else.

However, this process of producing specific antibodies takes some time, typically 1-2 weeks. During this intervening period of 1-2 weeks, we are ill, and with some infections we may suffer from serious complications during this period (Some life-threatening infections like polio can even lead to death in this period). But once the antibodies are formed, they kill/ defeat the invader and we recover. Also, some of the cells that form antibodies become “memory cells” and they remain in our body lifelong, to help us in any future infection by the same virus/ bacteria. Our body has a repository (“library”) of billions of such memory cells: each one for a specific virus/ bacteria. In case of invasion by the same virus/ bacteria again, the specific “memory cells” are activated immediately (the time of 1-2 weeks is not required) and the virus or the bacteria is destroyed even before it makes us sick. This is something that is exploited in vaccinology (vide infra, Q. 3.)

This animation by University of Oxford explains the whole process beautifully.


Q. 3. How do vaccines work?

A. Vaccines act by mimicking the above process of real invasion by bacteria or the virus and lead to development of antibodies specific to that particular bacteria or the virus.

Different type of vaccines work differently, but here I would limit myself to two common types of vaccines that are relevant here with respect to polio vaccines: “live attenuated” vaccines and “killed” vaccines.

In live attenuated vaccine, the virus or the bacteria is “attenuated” (attenuated means weakened). This concoction of live but weakened virus/ bacteria is in the vaccine. This weakened bacteria or the virus, when enters the body cannot lead to disease, but the immune system automatically treats it as an “invader” and mounts an immune response leading to development of specific antibodies. Some of these antibodies become so called “memory cells” and are stocked in the “library” of all types of antibodies. Hence, in case the real (“wild”) virus or the bacteria enters the body of a vaccinated person, the immune response (antibody production) is extremely prompt (Thanks to the memory cells already there because of vaccination).  Thus, the virus or the bacteria is promptly neutralized, and the vaccinated baby/ child/ adult is saved from the disease.

Oral polio vaccine (OPV) is this type of vaccine, containing “live attenuated” viruses. Since the viruses are live, they multiply in body (which amplifies the antibody production), just like wild viruses and are shed in stools of vaccinated baby/ child. Being an oral vaccine, it is easier to administer. It also gives better “gut immunity” that is important, since the real virus also enters through gut (intestine). However, it is less effective than inactivated (injectable) polio vaccine…hence a baby requires repeated doses of OPV to be effective. 

In killed vaccine, there is “killed” bacteria or the virus. When administered, immune response is mounted as the immune system considers it as an invader and antibodies and “memory cells” are formed (as with live vaccine). The IPV (inactivated polio vaccine) that is the injectable vaccine against polio is this type of vaccine. It contains killed polio viruses. This vaccine needs to be injected, gives less gut immunity and is costlier on dose-to-dose basis. However, it is much more effective than OPV.

OPV and IPV complement each other due to their specific properties, and giving both OPV and IPV as per the standard recommendations gives excellent protection against polio.

Q. 4. Are there different types of polio viruses?        

A. Yes, there are 3 types of polio viruses. These are designated as Poliovirus type-1, Poliovirus type-2 and Poliovirus type-3, or in short P1, P2 and P3. All the three are distinct viruses, but cause identical disease. Antibodies against one type of poliovirus kills only that type of virus. Hence, to prevent polio disease, we need antibodies against all the three types of viruses.


Q. 5. What is National Polio Eradication Program?

A. Following the launch of Global Polio Eradication Initiative (GPEI) by World Health Organization (WHO) in 1988, India launched National Polio Eradication Program (NPEP) in 1995 with an aim to eradicate the disease completely by vaccinating all kids below 5 years of age. The most crucial and most visible component of this is Pulse Polio strategy, under which all kids between 0 and 5 years of age are given OPV on pre-designated days. These are planned on Sundays and are called “Polio Ravivars”.  The success of the program can be judged from the fact that annual number of polio cases have fallen from thousands to NIL. The last case of Polio in India was reported on January 13, 2011. Similar programs in all over the world have led to elimination of the disease from most countries. From estimated 3,50,000 cases globally in 1988, only 22 cases were reported globally in 2017. Only three countries (Afghanistan, Pakistan and Nigeria) are reporting polio cases now. The polio eradication program needs to be continued vigorously till the disease is globally eradicated like small pox (Small Pox was eradicated in 1977, and we don’t need vaccination against that now).

It is also to be noted that out of 3 types of polio viruses, poliovirus type-2 was globally eradicated in 1999. Last case of type- 3 was reported in 2012 in Nigeria. All the cases after that are by type-1 poliovirus only. Since the OPV has live (although attenuated) viruses, it is also planned that this would be withdrawn systematically so that no form of polio virus remains in society after eradication. As per this strategy, it was decided by WHO to eliminate type 2 of polio viruses from OPV globally, since it has been a long time since the disease by that type was reported from anywhere in the world. Hence, bivalent OPV (bOPV) was manufactured globally that contained vaccine viruses of only type 1 and 3. After having adequate stocks of this, it was decided that after April 25, 2016, only bOPV would be used everywhere and all existing stocks of tOPV (trivalent OPV with all the three types of vaccine viruses) would be destroyed from everywhere. This was done successfully, and after this date we all have been using bOPV only. All the existing stock of tOPV with us was returned to the authorities and was destroyed. Similarly, all the stock with the pharma companies, in transit and elsewhere was destroyed. 

This is something that is crucial to understand the current issue. While all OPV before 25th April 2016 had all the three types of vaccine viruses, all the OPV that is being used after this have only type 1 and 3 vaccine viruses.

It is planned that type 3 would also be withdrawn similarly in future and ultimately, OPV would be totally discontinued.

For complete protection from polio, IPV is also being given to all babies. IPV continues to provide protection against all the three types of polio viruses (Since IPV has killed viruses, there is no problem with continuing with all the three types).

For the success of the polio eradication program, there are many other components/ strategies, in addition to Pulse Polio rounds. This includes surveillance. For this purpose, stool samples of cases that are even remotely similar to polio are tested for polioviruses in WHO-accredited reference labs. In addition, sewage samples are also tested for polio viruses all across the country to keep tab on the virus on community level. Around 80,000 stool samples are collected and tested annually in addition to sewage samples from 45 sites across the country.



With the above knowledge, now it would be bit easier to understand the current controversy.

The issue was picked up by the surveillance component of National Polio Eradication Program (NPEP). Routine testing of sewage samples and stool samples in state of Uttar Pradesh (UP), type-2 vaccine viruses (not disease causing wild virus but attenuated vaccine virus) was found. Further investigation revealed the source of the virus to be a particular batch of OPV that was been used in four districts of UP under the Govt program. The fact that the “contamination” was picked up soon after the vaccine was administered shows the strength of our surveillance strategies under NPEP. That particular brand (all batches to be on safer side, not just the affected batches) of the OPV was immediately discontinued. It is also to be noted that the amount of type-2 viruses in the said batch of the vaccine is reported to be very low. However, since type-2 vaccine virus is not being used for more than 2 years, it is a matter of investigation how the vials of bOPV were contaminated with type-2 virus.

Thus, it is clear that the issue at hand is not at all a safety issue for any baby, but a   technical issue with a bearing on the eradication program. The authorities are pursuing the issue accordingly.

The Govt. also issued press release on October 4, 2018 to quell the unnecessary rumours. Here is the link for the press release.


The bottom line is, “The risk of not vaccinating a baby is much much much more than not vaccinating because of this technical issue with the vaccine. The vaccine continues to be life-and-limb saving vaccine”.


Although I have tried to simplify a complex issue so that parents can understand it. However, being a highly technical issue, I do understand that parents might wish to have more clarifications. Please feel free to mail me on for any information related to any aspect of the issue. Expect a reply in 72-96 hours. Thanks and Regards, Dr. Puneet Kumar.