The Government has no information regarding polio cases!
Dr Yash Paul, Jaipur
Last polio case by wild poliovirus labelled as confirmed polio case was reported on 13th January 2011 and in March 2014 India was declared poliofree country. Ninth week 2014 (March 1, 2014) report showed that in 2013 there were 54846 AFP cases, no confirmed polio case, 5 VDPV cases, 17 polio compatible cases, 52993 had been discarded as non-polio cases, and 1831 cases were still pending i.e. under investigation. Later in 16th week number of Polio compatible cases rose to 23. Since then NPSP stopped publishing Weekly Report on its website: www.npspindia.org/.
On 10th February 2016 I had sought information under RTI Act 2005 regarding the number of VAPP, polio compatible and VDPV cases which had occurred in India from 1st January 2011 to 31st December 2015. A letter from Ministry of Health & Family Welfare Immunization Division, Government of India No. Z.33013/02/2016-Imm/dated 8th March, 2016 stated:
1. Please refer to your RTI application dated 10.02.2016 seeking information under RTI Act, 2005. In this regard, it is informed that no data on polio compatible case / cases with VAPPs is maintained by this Ministry. The data on polio compatible case / cases with VAPPs is maintained by WHO and uploaded on their website from time to time.
2. In case you are not satisfied with reply an appeal can be made to Director (RCH), Ministry of Health & Family Welfare who is the appellate authority in this matter.
On 18th March 2016 I had sent a memorandum to the appellate authority where I had pointed out: "Surprisingly Ministry of Health & Family Welfare is not aware of the fact that NPSP has stopped displaying figures regarding polio cases since India had been declared polio free. NPSP has never posted number of VAPP cases on its website. More over it has now removed the information regarding past polio incidence. Still the Ministry has advised the author to check WHO Website."
Response from the Appellate Authority dated 8th April 2016 stated: 'Having considered the appeal of the appellant and the record available, I am of the considered view that the requisite information in respect of Immunization Division as available and admissible under the RTI Act, 2005 has already been provided to the appellant by the CPIO (Central Public Information Officer). In the light of above, the appeal of the appellant under Section 19(1) of the RTI Act, 2005 w.r.t. Immunization stand disposed off.' The Appellate Authority had stated further: "If the appellant is not satisfied with this order, he may appeal to the Central Information Commission......"
I was fully satisfied that the Ministry of Health & Family Welfare is not hiding any information, as it has admitted that it has no information regarding polio cases caused by OPV, though; this information was available to public on WHO/NPSP website. Ministry is also not aware of the fact that NPSP has not only stopped posting of AFP data since India had been declared polio free, but also removed the past data from its website. Thus, I found no reason to approach Central Information Commission.
Dr. Yash Paul
G-1, Kumkum Apartment-II,
48, Vinoba Nagar,
Malviya Nagar, Jaipur-302017
Violation of human rights during polio eradication
Polio eradication program in India was started in 1995, though belatedly last polio case by wild polio virus was reported on 13th January 2011, it is a great achievement. We all should acknowledge and appreciate the tiring but selfless hard work by millions of citizens in administering OPV to millions of under five children time and again. We should also acknowledge the role played by the World Health Organization (WHO) and the contributions made by many national and international donors specially Mellinda Gates Trust and Rotary International. Indian Academy of Pediatrics also participated in this national project. During this program some wrongs were done which should not be overlooked, so that such incidences may not occur in future.
In 1988 the World Health Assembly, during its 41st meeting passed resolution 28, declaring that "World Health Organization (WHO) takes initiative for global eradication of polio exclusively by OPV". This resolution is known as WHA-41.28.
The scientific information regarding OPV (oral polio vaccine) available at that point of time i.e. 1988 was as following :
1.It can cause paralysis in vaccine recipients. It is called vaccine associated paralytic poliomyelitis (VAPP), which in fact is polio disease caused by OPV. It occurs because polio vaccine viruses sometimes back-mutate and re-acquire property to cause disease.
2.Secondary spread of these mutant neurovirulent vaccine polioviruses can cause VAPP in close contacts ie. some persons may develop disease without taking OPV themselves.
3.Some children, specially from tropical and developing countries, show poor response to OPV and may develop polio disease by wild polioviruses despite taking many doses of OPV. India qualifies on both kinds.
But, the cost factor, ease of administration, as it is given by mouth were important reasons for choosing OPV.
A move in the direction of providing the WHO with more oversight and regulatory power was taken on 23 May 2005 with the revision of International Health Regulations (IHRs), thereby signaling ‘remarkably increased willingness by member states and the organization itself to assert WHO authority not only in coping with emergent, serious communicable disease threats and outbreaks, but also in establishing a firmer international legal basis for international scientific cooperation towards that end,’ . Thus, Government of India was expected to participate in this global polio eradication program. But, the Government cannot absolve itself of its responsibility regarding welfare and safety of the children.
It is presumed that pre-launch evaluation of every program is done regarding feasibility, acceptability and relative benefits and harms which would accrue from a program. Such evaluation must have been done for global polio eradication program.
There is also a need for periodic ongoing evaluation of program to assess if the program is providing high benefits. In case it is found that less benefits or more harm is occurring, honest re-evaluation of the whole program should be done; and if needed the program be suspencled for some time or even abandoned. Polio eradication program was launched in India in 1995 and eradication was expected to occur by year 2000. Last polio case by wild polio virus was reported on 13th January 2011 ie. eleven years later. No attempts were made by the experts to find reasons for failure and delay in polio eradication. People were blamed that they were not participating in the program i.e. not letting their children be administered OPV drops during the Pulse Polio Program.
National Polio Surveillance Project is presently the only agency in the country which collects data for children upto 15 years of age regarding polio cases in India. National Polio Surveillance Project (NPSP) classifies polio cases in following groups:
1. Polio cases caused by wild polio viruses, these are called confirmed polio cases.
2. Polio cases caused by mutant vaccine viruses in OPV called VAPP cases.
3. Polio cases where it could not be determined whether polio was caused by wild polio viruses or by vaccine polio viruses contained in OPV are called polio compatible cases.
4. In case mutations in vaccine viruses contained in OPV progress further, these behave like wild polio viruses in capacity to spread and cause disease. These are called vaccine derived polio viruses (VDPVs) cases.
The author would like to take up the issues of human rights violations which occurred during polio eradication compaign in India.
1. Polio disease caused by OPV is not considered polio disease.
An enquiry instituted by WHO having Albert Sabin the maker of OPV and other 34 international experts concluded that OPV can cause paralytic polio disease . An acute flaccid paralysis (AFP) case who fulfills all the clinical criteria (parameters) to be labelled as a case of poliomyelitis, where no wild poliovirus is detected in two adequate samples of faecal matter, but vaccine poliovirus is detected should be considered a case of vaccine associated paralytic poliomyelitis (VAPP). Simply put, it is a case of polio disease caused by OPV. It is pertinent to state that enquiry was instituted by WHO and published in year 1976 in Bulletin of WHO.
In India those children who develop polio disease by OPV are not considered polio cases which is not only unethical but unscientific also. On page 713 of July 2013 issue of Indian Pediatrics, the official journal of the Indian Academy of Pediatrics in section 'News in brief' under subhead 'Polio in Maharashtra' it was stated: A(n) 11 month old child has been confirmed to have vaccine derived polio virus (VDPV) in the Beed district of Maharashtra on June 1st 2013. This is the third case of VDPV since March 2012 and the first in Maharashtra. There is a suspicion of underlying immunodeficiency in the child since he has been suffering from prolonged bouts of illness. India will not forfeit the polio free label because of this since VDPV is not enumerated in wild polio numbers .
In the March 1999 issue of Indian Pediatrics the author had stated: In our enthusiasm to eradicate Poliomyelitis, perhaps we are over-looking the fact that Oral Polio Vaccine has some relative and some definite contraindications ............. It should not be administered to a child with immunodeficiency and also to a child who is in close contact of a person with immunodeficiency. Such children should be administered Inactivated Polio Vaccine (IPV) . In year 2013 IPV was available, still the above mentioned child was administered OPV, who developed polio disease but would not be considered a polio case.
It is necessary to provide information regarding 'Polio Compatible' cases. As stated earlier any child upto the age of 15 years who develops weakness in any part of body is reported to NPSP as a case of acute flaccid paralysis (AFP). Surveillance Medical Officer (SMO) of NPSP of that area examines the child, collects all information and obtains two samples of faecal matter within two weeks of onset of paralysis. In case both stools are negative for wild polioviruses and vaccine polio viruses, or faecal matter could not be collected but after excluding other causes of paralysis like Guillain Barre Syndrome, Transverse Myelitis etc., the child fulfils all the parameters to be labelled as polio case, it is classified as 'Polio Compatible' case.
It can be seen in Table 1 that number of Polio Compatible cases has been high. There may be lack of medical facilities in urban slums and rural areas, parents may not take the affected child to medical facilities, but may approach a 'faithhealer' or take the child to places of worship for blessings of gods. Thus such a case may come to notice of NPSP quite late.
It is great irony that VAPP cases are not mentioned in case classification by NPSP, there is no column for VAPP cases. VAPP cases are discarded as non-polio cases, and 'polio compatible' and VDPV cases are not counted as polio cases as has already been stated.
2. Compensation for Polio cases
In any mass public health program some participants may not derive benefits due to some reasons, but, harm should not occur to any participant. The fact that OPV may cause polio disease in some children was not disclosed to the people so that parents may not refuse to administer OPV to their children. Question arises: Was it a justifiable policy decision? Answer is: It was not only right policy, but, it was necessary also. It is a harsh reality that there is low vaccine coverage in India, many children do not receive any or complete doses of different vaccines during the childhood. In case had this information been made public, many parents would have refused to administer OPV.
However, if it is indeed to be accepted that the benefits of polio eradication outweigh the with-holding of information about the risks of harm, then at the very least, an adequate compensation scheme should have been formulated. Natural justice demands this . But, instead of providing some mechanism to provide compensation to these children who develop polio disease by OPV the Government of India punished the families who refused OPV administration to their children.
The Governments give compensation to affected persons or their families following accidents and calamities. Every person who develops harm due to failure of a drug or adverse drug reaction is entitled for damages and compensation from Pharma industry or medical personnel or the hospitals. Why should the children who have been harmed by OPV and affected by life long disability be deprived of any legitimate compensation on the ground that this polio eradication program was part of a global program under aegis of WHO ?
On 22nd December, 2005 the author had presented a memorandum to Dr. Anbumani Ramadoss, the then Health Minister, Government of India, with copies to the Secretary, Ministry of Health & Family Welfare and Shri Girdhari Lal Bhargava, the then Member of Parliament from Jaipur, but received no communication from any one. On 20th May 2013, the author had sent a memorandum regarding compensation to polio cases to Shri Ghulam Nabi Azad, the then Health Minister, Government of India, but did not receive any acknowledgement or response. On 5th August 2013, the author sent similar memorandum to the Secretary, National Human Rights Commission, New Delhi. A letter from the National Human Rights Commission dated 30th August, 2013, reference No. 1977/20/0/2013 was received informing that the memorandum has been forwarded to the Ministry of Health, Government of India, but received no further response from the Ministry of Health, Government of India or the National Human Rights Commission.
On 6th October 2014, the author sent a petition to the Council of State (Rajya Sabha), Parliament House for consideration of compensation to those children who had developed polio disease during the polio eradication program. A letter from the Ministry of Health and Family Welfare, Ref. No. Z-33011/03/2014-LLSV dated 13th February, 2015 was received. It stated: "Under the Public health system established in India, all types of Acute Flaccid Paralysis Cases, whether polio or non-polio, are provided free medical care at all health facilities including corrective surgery, regular physiotherapy and rehabilitation."
It is a right idea to provide above mentioned facilities to all people with disability because of polio disease or other reasons. Disability in persons due to non-polio conditions include congenital anomalies (birth defects), birth injury, neonatal asphyxia, neonatal infections, Kernicterus and many more reasons in a newborn baby which may result in permanent disability. Such disabilities can occur later also because of brain infections, brain injury, accidents etc. During the polio eradication program every case of polio disease who has developed disability, it is because he/she had participated in polio eradication program so rightfully deserves appropriate compassion and compensation, and such children should not be labelled as 'price paid' for the national program. Even a soldier's death is treated differently if he dies fighting enemy than a soldier who dies because of accident or illness.
Why Compensation ?
1. Every child who has not been administered OPV drops or IPV injection may not develop polio disease. The child may not be infected by wild poliovirus or if infected may not develop paralytic disease; about 1% of infected persons develop disease, unlike small pox disease where all developed disease.
2. Any child who has received age appropriate number of OPV doses should not develop polio disease. During the Polio Eradication Program many children had developed polio disease even after taking many doses of OPV as can be seen in Table 2.
3. No child should develop polio disease because of OPV. Many children had developed polio disease classified as VAPP cases or VDPV cases. Both are not considered polio cases in India. Number of VAPP cases has never been displayed by National Polio Surveillance Project (NPSP) on its website - www.npspindia.org/
This means that many children had developed polio disease because either OPV caused the disease or failed to provide protection against the disease.
Who is eligible for Compensation?
Pulse polio immunization program was started in India on 2nd October 1995. As no proper records of vaccintion are maintained, every child living in India and born on or after 2nd October 1995, should be presumed to have received OPV doses during every pulse polio round. Thus, any child who was born on or after 2nd October, 1995, and has developed residual paralysis due to wild polio virus or vaccine polio virus should be entitled for compensation.
3. Punishment for Refusing OPV Administration
Hindustan Times dated August 14, 2007 carried news with caption 'Refuse polio drops, lose power and ration cards'. It stated: "In what appears to be a first in Uttar Pradesh, the polio drive is sending a clear message to the people: refusing polio drops will cost them dear. At least two people in the district have had their ration cards cancelled and the power supply to their homes cut for saying no to the immunisation of their children." Is penalising for refusing OPV administration lawful and ethical? The answer is: It is unlawful and unethical.
Immunisation against particular disease(s) is compulsory in a number of countries. Punishment for non-compliance include fines or imprisonment for the parents and refusal of school admission for the children. Compulsory immunisation could be justified on the grounds that it promotes the overall health of the population, the common good. This argument cannot be applied to make OPV administration compulsory because it may cause paralysis in some children, and on the other hand it may fail to provide protection to some children who may develop paralytic disease by despite taking many doses of vaccine.
On September 3, 2007 the author had sent a Memorandum to the National Human Rights Commission, New Delhi, salient points are stated here.
OPV administration has not been declared compulsory. People or the parents of children have a right to refuse a vaccine which has been mandated as compulsory, they have to give reasons for refusal and would be responsible for any harm occurred to them or their family members because of non-vaccination. In the above instances OPV was being forced and penalty imposed for non-cooperation.
A child may not develop polio disease even if the child has not received any polio vaccine. On the other hand a child may develop polio disease despite taking many doses of OPV, because either OPV had failed to protect the child or had actually caused polio disease, which is called vaccine associated paralytic poliomyelitis (VAPP). It can be seen in Table 2 that 2004 onwards percentage of polio cases who had taken more than 7 doses of OPV increased. No caring society and welfare government should condone FORCED administration of OPV which is neither very safe nor very effective, the facts which are known to the experts all over the world.
Through this memorandum following remedies are sought from the commission :
1. Forfeited ration cards be returned and the electric power connections be restored to the affected house-holds.
2. Appropriate actions be taken against those who in their misguided over enthusiasm have caused inconvenience and hardships to these families.
The complaint was placed before the Commission on October 8, 2007. Commission in its letter dated October 10, 2007 forwarded the complaint to the Secretary, Deptt. of Health & Family Welfare, Govt. of Uttar Pradesh, Lucknow. Copy of this letter was sent to the author on March 26, 2008, ie 5½ months later. Reminders were sent to the commission on 23rd April 2008 and 26th May 2008 to know about the status of the case, but there was no response.
Author raised this issue with Medico-legal group of Indian Academy of Pediatrics regarding: (1) Can the parents or caretakers of the children upto 5 years of age be penalised by the local authority or prosecuted in the court of law if they refuse administration of OPV during Pulse Polio Immunization? (2) Can such punitive action be taken against a doctor who does not administer OPV to those children who have received IPV to avoid any risk of VAPP in close immunocompromised contacts? . Dr. Mahesh Baldwa and Dr. Satish Tiwari, both child specialists and law graduates stated: All the national health programs need to have persuasive tone and should never have coercive tenure. Coercion may arrogate with fundamental right enshrined in Article 21 of Constitution of India . Many doctors carry the impression that if they say any thing against OPV or some aspects of polio eradication program they will be punished by the government.
Note : On 20th January 2014, the World Health Organization (WHO) declared India polio free country. After some time NPSP not only stopped updating polio data on its website www.npspindia.org; but also removed the post data from its website.
1. Baldwa M, Tiwari S. (2009) Punishment for Refusing OPV (Reply). Indian Pediatr; 46: 540 - 541.
2. Passi GR (2013). News in brief. Indian Pediatr, 50: 713.
3. Paul Y. (1999) Contraindications of OPV. Indian Pediatr; 36: 318 - 319.
4. Paul Y, Dawson A. (2005). Some Ethical Issues Arising From Polio Eradication Programmes in India. Bioethics, 19; 4: 393 – 406.
5. Paul Y. (2009) Punishment for Refusing OPV. Indian Pediatr; 46: 540.
6. Schatz GC. (2005). International Health Regulations: New Mandate for Scientific Cooperation. ASIL Insight 2 August 2005 (http://www.asil.org/insights/2005/08/uinsight050802.html).
7. WHO Consultation (1976). The relation between acute persisting spinal paralysis and poliomyelitis vaccine (oral): Results of a WHO enquiry. Bull WHO; 54: 319 - 331.
Ignorance about law is punishable, but ignorance about science is not!
Some exaggerated and non-existing properties of OPV are being taught
No one can claim that he/she did not know that red light at traffic signal means - STOP, so he / she should not be punished. Any one ignorant about knowledge can not be punished. There are many people and groups who still believe that the sun revolves around the Earth, and the Earth is flat. You may laugh at them, may try to educate them if they are willing, but can not punish them.
No school, college or university teaches anywhere that the sun revolves around the Earth. But, strangely students in medical colleges all over the country are being taught some exaggerated or non-existing properties of oral polio vaccine (OPV) since long time.
In October-December 2005 issue of Indian Journal of Community Medicine on page 152,1 I had stated: I seek comments from Dr. (Mrs.) Park, the learned author of Park's Textbook of Preventive and Social Medicine, regarding some of the properties or advantages of oral polio vaccine (OPV) as mentioned in the text book. On page 164 of the eighteenth edition (2005) of the textbook it is stated: "The vaccine progeny is excreted in the faeces and secondary spread occurs to household contacts and susceptible contacts in the community. Non-immunized persons may therefore, be immunized."
Different studies from 1959 onwards had demonstrated that this herd effect was very low to be of any clinical value.2-10 These include studies by Dr. A.B. Sabin6 the original maker of OPV and WHO7. The WHO study had stated: "These observations cast doubt on the importance of indirect spread of vaccine virus in raising overall levels of humoral immunity to poliovirus types 1 and 3, at least during the first 6 months of life...."
The herd immunity caused by OPV is not widespread but, is negligible because of two reasons: (i) Attenuated (modified) polioviruses contained in OPV have markedly reduced infectivity, resulting in infrequent transmission from vaccinated children to contacts, and (ii) low load of vaccine viruses spread through faeces. There are about 10 lakh (1 million) type 1 polioviruses, about 1 lakh (0.1 million) type 2 polioviruses and about 6 lakh (0.6 million) type 3 polioviruses i.e. about 17 lakh (1.7 million) vaccine polioviruses in each dose of two drops of OPV. On the other hand one gram of faecal matter contains about 100 polioviruses.8 Thus 17 kg of faecal matter of vaccinated children will provide same quantity of vaccine polioviruses as are contained in one dose (two drops) of OPV. It has been observed that in India many children have developed paralytic poliomyelitis even after taking ten or more doses of OPV. How much antibodies would be generated by few thousand vaccine polioviruses spread through faeces when many doses of OPV, each dose containing 1.7 million vaccine polioviruses have failed to generate protective immunity?
Further it is stated in the textbook: "This property (herd immunity) of OPV has been exploited in controlling epidemics of polio by administering the vaccine simultaneously in a short period to all susceptibles in a community." The study by Nightingale quoted in the textbook had stated: "The OPV was favoured because of its ease of administration (oral instead of injected), expected long lasting immunity, and the production of bowel immunity, which in turn would lead to interruption in the chain of transmission of wild viruses from population"9. This issue had been elaborated further by Melnick, again quoted in the textbook: "Because the live vaccine viruses become established quickly in the alimentary tract of the vaccine recipient, they are capable of blocking infection with epidemic virus strain within a matter of days even before the vaccine-induced antibody becomes fully effective"10. This property of quick establishment in elimentary tract makes OPV superior to IPV during epidemics, and not the herd immunity caused by OPV.
It is further stated in the textbook: "This procedure (administering OPV simultaneously in a short period to all susceptibles in community called Pulse Polio Campaign) virtually eliminates the wild polio strains in the community and replaces them by attenuated strains." I had failed to find any study or reference which supported the argument that vaccine polioviruses replace wild polioviruses. I raised this issue with the viorlogists, who stated: "It is primarily a question of which virus gets access to the host first. If the child is first exposed to the vaccine strains then the vaccine strain would cause gut immunity and systemic immunity against poliovirus, causing large proportion of the previously susceptible population to be thus immune. It will break the natural cycle of transmission of wild poliovirus at a community level. In a given individual the vaccine virus, if given after the exposure to the wild virus, will not replace the former"11. Thus, repeated doses of OPV are given not to replace wild polioviruses, but to replace susceptible non-immune population with immune population, so that wild polioviruses may not find suitable host to replicate (multiply) and this will eventually abolish the wild poliovirus circulation.
Dr. (Mrs.) Park did not respond to the issues raised by me1, some other academician had responded which was published on page 153:12
Is this spread (of vaccine viruses) in the community sufficient enough to immunize the close contacts?
There are two references:
1. Oral polio vaccine is shed from the gut of an immunized individual, providing consistant boosting to the community, whilst also preventing carriage of wild virus.13
2. Secondary spread of vaccine plays a modest role in increasing the polio immunity in inner city populations, especially against types 1 and 3.14
However the exact quantification of OPV coverage (eg 66%) is not verifiable from any source. Out of three references quoted by Dr. Park, only two could be obtained. This information was not available in those references.
Can vaccine polio viruses replace wild polio viruses?
In an individual the vaccine virus, after the exposure to the wild virus, will not replace the former. So pre-emptive intervention with the vaccine regularly in the community reducing the build up of susceptible individuals (children) will eventually abolish the wild virus circulation as it appears that humans are only natural reservoirs of infection. Hence according to the available evidence OPV cannot displace the wild polioviruses from the gut.
The expert agreed that (i) widespread "herd immunity" does not occur with OPV and (ii) Vaccine polio viruses can not replace wild polio viruses.
There were about 250 medical colleges at that point of time (2005), no teacher or any research scholar had cared to check or verify the authenticity of the contents stated in the book, till I raised these issues in Indian Journal of Community Medicine, the official publication of Indian Association of Preventive and Social Medicine. The academician did not disclose her/his name.
Question may be asked: Why have I raised this issue in 2016, almost a decade later? Park's Textbook of Preventive and Social Medicine continues to carry same wrong information even now. Same text is published on page 207 of 23rd edition (2015) of the book. Presently there are more than 500 government and private medical colleges in the country. No teacher from the department of Preventive and Social Medicine has paid attention, including the academician who had responded to the issues raised by me in year 2005 and members of the Editorial Board for year 2005 of Indian Journal of Community Medicine. No one has questioned the author of the textbook for giving some wrong information regarding OPV which is being taught to the medical students in India.
On 25th December 2015, I had raised this issue with the Medical Council of India, New Delhi, along with copies to the Secretary Generals of Indian Association of Preventive & Social Medicine, Indian Medical Association, and Indian Academy of Pediatrics, sent reminder on 25th February 2016. On 2nd April 2016, I raised this issue with Heads of Department of Community Medicine of two prime Medical Institutes. I have not received any response from any quarter which would clarify which is correct: (i) contents of the textbook under question or (ii) statement of anonymons expert ?
Dr. Yash Paul
G-1, Kumkum Apartment-II,
48, Vinoba Nagar,
Malviya Nagar, Jaipur-302017
1. Paul Y. Some Exaggerated or Non-existing Properties of OPV. Indian Journal of Community Medicine 2005; 30(4): 152.
2.Gerd S, Bottiger M, Logercruntz R: Vaccination with attenuated poliovirus type 1, the CHAT strains of the natural spread within families of living vaccine strains of poliovirus. In: First International Conference on Live Poliovirus Vaccines. Washington DC: Pan American Sanitary Bureau 1959; 350-54, special Publication 44.
3.Gelfand HM, Potash L, Le Blanc DR, Fox JP. Revised preliminaryreport on the Louisiana observations of the natural spread within families of living vaccine strains of poliovirus. In: First International Conference on Live Poliovirus Vaccines. Washington DC: Pan American Sanitary Bureau; 1959; 203-217. Special Publication 44.
4.Horstmann DM, Niederman JC, Paul JR: Attenuated type 1 poliovirus vaccine: Its capacity to infect and to spread from vaccines within an institutional setting. JAMA 1959; 170: 1 - 8.
5.Johnson EA, Cooney M: Minnesota studies with oral poliomyelitis vaccine: Community spread of orally administered attenuated poliovirus vaccine strains. In: Second International Conference on Live Poliovirus Vaccines. Washington DC: Pan Americal Sanitary Bureau 1960; 161 - 73. Special Publication 50.
6.Sabin AB, Michales RH, Spigland I et al. Community wide use of oral poliovirus vaccine. Americal Journal of Disease of Children 1961; 101: 546 - 567.
7.World Health Organization Collaborative Study Group on oral poliovirus vaccine. A Prospective Evaluation in Brazil and the Gambia. Journal of Infectious Disease 1995; 171: 1097 - 1106).
8.Onorato IM, Modlin JF, Mc Bean AM, Thomas ML, Lossosky GA, Bewnier R. Mucosal immunity induced by enhanced potency IPV and OPV. J Infectious Disease 1991; 163: 1 - 6.
9.Nightingale EO. Recommendations for a national policy on poliomyelitis vaccination. New England Journal of Medicine. 1977; 297: 249 - 253
10. Melnick JL. Advantages and disadvantages of killed and live poliomyelitis vaccines. Bulletin of WHO 1978; 56: 21 - 38.
11.Paul Y, Sridharan G, Abraham P. How do the vaccine polio viruses replace the wild polio viruses? Indian Journal of Medical Microbiology 2002; 20: 56
12.Anonymus. Some Exaggerated or Non-existing Properties of OPV (Reply). Indian Journal of Community Medicine 2005; 30(4): 153.
13.Bedford H, Ellison D: Misconceptions about the new combination vaccine. Editorial BMJ. 324: 411 - 412.
14.Chen RT, Hausinger H, Dajani AS et al. Seroprevalence of antibody against polio virus in inner city preschool children. Implications for vaccination policy in the United States. National Immunization Programme, Centre for Disease Control and Preventionb, Atlanta, GA30333, USA.