POLIO ERADICATION SUCCESS AND SETBACKS OF GLOBAL VACCINATION

Transcription

1 POLIO ERADICATION SUCCESS AND SETBACKS OF GLOBAL VACCINATION Polio The Virus Poliomyelitis, commonly referred to as polio or even Infantile Paralysis, is a virus that causes the gray matter of the spinal cord to become inflamed. There are three strains of polio, classified as Type I, Type II and Type III. Contrary to conventional wisdom, the polio virus does not directly cause the paralysis that is associated with it. The vast majority of individuals who contract polio likely do not even realize they have it. It typically presents with only mild respiratory or gastrointestinal symptoms, fever, headache and muscle stiffness; symptoms which most people would associate with a case of the flu. Presentation of these symptoms is typically referred to as non-paralytic polio 1. The more serious of polio or true polio that most people equate with the disease causes weakness or paralysis of muscles which is often permanent. In this type of presentation, the virus invades the central nervous system, attaching to protruding proteins on motor neurons, or nerve cells, in the anterior horns of the spinal cord and brainstem. The inflammation causes damage to the nerve cells which results in tightness, weakness and paralysis of muscles, usually in the neck, back and hamstring muscles of the leg. Many affected individuals improve after the infection subsides, but for many the motor neurons have been so severely damaged or destroyed that the weakness or paralysis is permanent. Some cases are so severe as to damage the motor neurons of the diaphragm and respiratory system, causing death from the patients inability to breathe. 2,3

2 Polio Vaccination 2 Polio is transmitted by faecal-oral contact. The virus is contracted orally and once in the intestines it multiplies and then is excreted in the intestines. It is then transmitted via contaminated water, where sewage and drinking water supplies are not adequately treated, or through contact with the faecal matter of an infected individual. Children are especially susceptible to transmission. 4,5 Historical Perspective Polio transmission and numerous outbreaks that rose to the level of epidemics have had a profound effect on modern medicine and spurred worldwide discussions on the wisdom and implementation of vaccinations and control of communicable diseases. Polio appears to have a long history with evidence of its existence dating back to the Egyptian era. Epidemics began appearing in Europe and then in the U.S. in the mid-1800 s. Prior to the 20 th century sanitation and sewage treatment was poor and babies were frequently exposed to polioviruses. However, because they also were breastfed, they received antibodies through their mother s breast milk, enabling their immune systems to develop their own antibodies. 6 Then in the 1940 s and 1950 s the polio epidemic in the U.S. reached a critical point with over 20,000 cases that rose to the paralytic condition of true polio. Improvements in sanitation that occurred during this period reduced people s initial exposure to the virus and also increased the age of exposure, resulting in more severe cases and even death. 7 Vaccine Development - Salk and Sabin The polio epidemic seemingly grew with every decade during the early years of the 20 th century. Smallpox, diphtheria, measles, and pertussis were also seen in epidemic proportions. Many first generation vaccines began to be used to combat the spread of communicable disease during this time. 8

3 Polio Vaccination 3 Dr. Jonas Salk began his career in immunology. While at the University of Pittsburgh, in 1947 he began researching poliovirus. He discovered that he could grow the virus in a cell culture rather than relying on monkeys to produce the virus. Then, in 1952 he developed a mixture of all three types of the virus. Using a chemical process that made the virus inactive he was able to develop a vaccine. The inactivated, or killed, polio vaccine (IPV) could be administered in an injection. Massive and urgent clinical trials began in 1954 in the U.S. and Canada. In 1955 the government readily approved the licensing of the vaccine for widespread distribution. The vaccine was determined to be 90 percent effective against Types II, and III and percent effective against Type I. Production facilities for the vaccine had already been built and were ready for production. Widespread inoculation began in the U.S., Canada and many European countries. 9 However, there were concerns about Salk s IPV vaccine. Many virologists were concerned that the inactivated virus would not be able to provide long lasting protection and that boosters would be necessary. Another issue that created concern was that almost 300 cases of polio and 10 deaths were attributed to vaccinations of the Salk IPV that contained incomplete inactivation of some of the viral particles. That production problem was soon corrected. But efforts to improve upon Salk s work continued. Albert Sabin at the University of Cincinnati developed a live attenuated vaccine that could be administered orally (OPV). It was believed that this vaccine would provide greater immunity than the injection, which would require boosters. However, conducting clinical trials of the Sabin vaccine was challenging as so many U.S. children were already receiving the Salk vaccine. Sabin took his trials to Northern Ireland, the Congo and the Soviet Union. By 1960 over 15 million children had received the Sabin vaccine. 8,9

4 Polio Vaccination 4 Sabin s vaccine offered longer immunity without boosters, acted quickly and was easier to administer. But a major benefit over Salk s vaccine was that it offered passive vaccination. Since the vaccination contained a live virus, it replicated in the bowel and a live attenuated virus was excreted. Thus in less sanitary conditions, the vaccine could actually protect those who had not been vaccinated in the same way that the virus was transmitted. By 1968 Sabin s OPV replaced Salk s IPV in the U.S., but many other countries continued to use Salk s vaccine. 9 One likely explanation is that switching back and forth between the two applications was not only costly, but would adversely affect public confidence in the vaccine. Additionally, if a country had already made significant progress in vaccination rates, it would be counter-productive to switch. Evolution from OPV to IPV However, work on both vaccines continued. New cases of paralytic polio were seen in the U.S. in individuals who had been inoculated with the OPV. It was determined that their conditions were consistent with the live virus regaining strength. Researchers in the Netherlands were motivated by their country s vaccination plan to combine the polio vaccination with vaccinations for diphtheria, pertussis and tetanus. In order to do so, the potency of the Salk vaccine would need to be improved. They were able to develop vaccines of any desired poliovirus concentration. As a result of improvements made in the Netherlands, U.S. children are once again being immunized with the new, improved Salk vaccine. The risk in the U.S. of contracting vaccine induced polio with the OPV is now greater than contracting polio through natural transmission, or wild polio.

5 Polio Vaccination 5 World Health Organization Strategy 1988 The World Health Organization, founded in 1948, is an agency of the UN whose mission is to maintain and improve worldwide standards of health. In 1988 the World Health Assembly launched The Global Polio Eradication Initiative. The organization successfully completed a similar effort to eradicate Smallpox in The World Health Organization continues to use the OPV in its vaccine packet of subsidized vaccines to poor countries because of its low cost, long term efficacy and ease of administration to patients. 9 Progress Toward Eradication Indeed, the effort has made significant progress; in 1988 there were an estimated 350,000 cases compared to 1,919 laboratory-confirmed cases in Only four countries, Nigeria, India, Pakistan and Afghanistan continue to see wild polio transmission.only six countries that were previously polio-free had reoccurrences in Three regions of the world have been certified as polio-free; the Americas, Europe and the Western Pacific. 12 The Wild Poliovirus Weekly Update published on April 25, 2007 reported that to date in incidents have been reported. 1,997 incidents were reported in Figure 1 Source: Global Polio Eradication Initiative 2005 Annual Report

6 Polio Vaccination 6 Obstacles to Eradication There are challenges to successful eradication of polio that were not present in the effort to eradicate smallpox, nor were they anticipated when WHO developed its strategy in The pathology of the virus and the existence of multiple strains of polio are unlike the single virus of smallpox. As vaccinations have been implemented and fewer incidents of naturally contracted polio are reported, most new incidents of polio result from activation of the live virus contained in the OPV. These strains have mutated over time and now require development of monovalent OPVs. Monovalent OPVs are vaccines which are generated from a single strain of the virus. Research and development of these new polio vaccines needs to be stepped up beyond current levels and made available to the population. 14 Use of the current trivalent OPV which is effective against all three types of virus in one application should be discontinued to prevent further mutations which might lead to new outbreaks. However, the technology for production capability for trivalent OPV cannot be eliminated. In the event it becomes necessary to treat an outbreak larger than the stockpiles of trivalent OPV, production may need to be resumed. In an article for Nature, David Heymann, Roland Sutter and R. Aylward, from the Global Polio Eradication Effort at the World Health Organization, stated that we urgently need to develop mopv for each of Type I, Type II and Type III as well as an IPV from poliovirus strains that are not from the wild virus. The risk of reintroducing the virus from a laboratory or manufacturing facility is also a concern. One incidence of polio in a child who had been inoculated was determined to have been caused by contamination from a laboratory accident where the father of the child worked. In fact, smallpox and sever acute respiratory syndrome (SARS) incidents have also been

7 Polio Vaccination 7 attributed to errors in laboratory practices. 200,000 laboratories, vaccination production facilities or other facilities have been identified with at risk materials for polio contamination. Outbreaks of vaccine derived poliovirus have occurred in many areas that were previously certified as being cleared of polio. These outbreaks were detected using a surveillance system established by the Eradication Initiative (Heymann). The surveillance system is designed to isolate the cause of acute paralysis. There are numerous viruses or conditions that can cause sudden paralysis in children under 15. Referred to as acute flaccid paralysis (AFP), it is imperative that the cause of AFP be determined promptly to rule out polio or confirm it. Prompt virological testing of faecal samples is used to disprove or confirm poliovirus infection. 15 There are 150 approved laboratories around the world to conduct surveillance testing (Heymann). Politics and economics also play an important role in compliance with the Eradication Initiative. Immunizations were suspended in Nigeria during due to rumors among many Muslims that the vaccinations were a western plot to inject chemicals into the population to cause infertility or HIV/AIDS. The rumors seem to have begun with some Islamic priests but gained credibility when the Nigerian government suspended the program and conducted independent testing on the vaccines. The vaccines were ultimately pronounced safe by the Nigerian government, but officials in Kano state reported that their independent tests indicated levels of hormones that reduced fertility. Kano, which had already had high levels of polio incidents, saw an even higher increase and strains that were known to originate in Kano spread to other regions of the country. 16 Leaders from WHO have since met with government and health leaders and most inoculations have resumed. But the damage to credibility and the spread of the disease had already created a great setback to eradication efforts in Nigeria.

8 Polio Vaccination 8 There is an additional concern that once eradication is complete and the individual risk of paralysis is eliminated, many developing countries who have limited funds and human resources will turn their efforts to other health concerns and will discontinue polio immunizations which will open the door for new outbreaks from reduced immunity or imported cases. Industrialized countries are likely to continue incorporating polio immunizations in their existing vaccination plans (Heymann). Increasing Focus on Vaccinations Industrialized countries are increasingly being targeted for criticism against an alarming increase in all vaccinations. In 1940 American children received 3 vaccinations for diphtheria, pertussis and tetanus. In 2000 they received up to 39 doses of 12 different vaccines. It is not unusual for a child to receive as many as nine doses in a single visit to the pediatrician One of the criticisms is the fact that many of the new vaccines are not for epidemics that occur in the industrialized world or in child populations. For example, children now receive 3 doses of the Hepatitis B vaccine, an infection that is found primarily among drug abusers and

9 Polio Vaccination 9 prostitutes. Critics argue that just because a vaccine is available does not mean that it should be automatically included in the mandatory schedule. Rather that, vaccines should be administered according to risk (Koch). Vaccine safety and public distrust of vaccination proponents is another major concern of vaccine awareness advocates. For example, brain damage and seizure associated with DPT vaccination were long considered a concern. Japan developed a safer version but the U.S. continued to use older, more profitable version for 15 years. The Japanese version was adopted in the U.S. in Also, In 1999 The FDA stated that vaccines expose infants to unsafe levels the neurotoxin mercury; used as a preservative in vaccines. Yet the Center for Disease Control which oversees U.S. vaccination protocol, recommended voluntary transition to mercury free vaccines to be implemented over time. High mercury exposure in children and infants with impairment in their ability to maintain glutathione defense is believed to prevent them from detoxifying and excreting the mercury toxins present in vaccinations, leading to impaired brain and nervous system development, resulting in learning disabilities, autism and other brain and cognitive disorders that are being increasingly diagnosed. 19 Along with concerns about genetically engineered foods, there is also concern over genetically engineered vaccines and vaccines produced from animal tissues. It is currently unknown if these might transfer unknown viruses or other diseases. Ronald Kennedy, professor of Microbiology and Immunology at the University of Oklahoma sums up the vaccine controversies rather well; There are too many hypotheses without scientific support. We need to support careful scientific investigation in this area, but unfortunately the federal government and the pharmaceutical companies don t agree and don t

10 Polio Vaccination 10 support such efforts. Executive Director of the American Association of Physicians and Surgeons, Jane Orient agrees. They are not doing the studies they need to do to put some of these fears to rest children receiving these immunizations really are experimental subjects. (Koch) Summary The controversies about overall vaccination rates and quality are likely to continue until scientific evidence can be brought to bear on the numerous hypotheses and speculation and confidence can be restored to pediatric vaccination programs. In the meantime, the worldwide efforts to eradicate polio will continue on a parallel track. As eradication of polio is achieved in other areas of the world and developing nations become more industrialized, their vaccination needs and patterns will change and it is likely that the current concerns of some industrialized nations will become global concerns. It seems that these are all issues that can be resolved with research and technology. Polio eradication, while still experiencing many challenges to success, does seem possible. The last remaining obstacles to most problems are usually the most difficult to overcome, which is why they remain until the last. Nevertheless, if funding and focus can remain strong for the development of monovirulent vaccines, containment, AFP surveillance and overcoming political opposition, it seems likely that we will see eradication of polio in our children s lifetime, if not in our own. In the meantime, it is imperative that science determine whether or not vaccine policy and quality concerns are valid and that the world health community establishes global guidelines for the use and range of vaccinations which can then be applied to all areas of the globe and can direct future efforts for disease eradication.

11 Polio Vaccination 11 References List 1 Polio s Legacy: An Oral History. Sass, E., Ed. (1996) University Press of America. Retrieved from on May 1, Site last updated February 19, Chamberlain, Neal PhD. A. T. Still University of Health Sciences/Kirksville College of Osteopathic Medicine. Retrieved from Retrieved on May 1, Site Last Revised 6/26/06 3 Smithsonian National Museum of American History Behring Center. Retrieved from May 1, Public Health Agency of Canada. Poliomyelitis. Retrieved from May 1, Site last updated October 12, Hull, H., Ward, N., Hull, B., Milstien, J., de Quadros, C., Paralytic Poliomyelitis: Seasoned Strategies, Disappearing Disease. The Lancet. Vol 34, May 28, pp Retrieved April 25, 2007 from Ovid. 6 Okonek, B. & Morganstein, L., ed. Development of Polio Vaccines. Access The National Health Museum. Retrieved from May 1, EMedTV Polio History Accessed May 1, Immunization Time Line. Retrieved May 1, Site Last updated July 1, Blume, S. & Geesink, I. A Brief History of Polio Vaccines. Science. 2 June, Vol no pp Retrieved from April 30, Global Polio Eradication Initiative Strategic Plan World Health Organization Printed in Switzerland. Retrieved from May 1, The Briefing Book on International Organizations in Geneva 2004, World Health Organization Retrieved from May 1, Global Polio Eradication Initiative Annual Report [WHO]. [report on internet]. Geneva, Switzerland. May, 2006 Retrieved from on May 1, 2007.

12 Polio Vaccination Wild Polio Weekly Update. April 25, [WHO]. [report on internet]. Retrieved from on May 1, Heymann, D., Sutter, R., & Aylward, R. (2005, April 7) A Global Call for New Polio Vaccines. Nature. Vol April, Retrieved April 25, 2007 from Academic Search Premier Database. 15 Continued surveillance for acute flaccid paralysis. World Health Organization Regional Office for Europe. Retrieved from May 1, NIGERIA: Muslim suspicion of polio vaccine lingers on. (March 2004). Science in Africa. [online magazine] Retrieved from on May 1, Koch, K. (2000, August 25). Vaccine controversies. CQ Researcher, 10, Retrieved May 1, 2007, from CQ Researcher Online, 18 Peltola, Heikki. (December, 2000). What Would Happen if we Stopped Vaccination? Lancet Vol. 356S. December p s22. Retrieved April 25, 2007 from Ovid Database. 19 EWG Report. Overloaded? Mercury and Autism (December, 2004). Retrieved from on May 1, 2007