Febuary 7, 2020

Editorial: Vaccine-Derived Polio Viruses Update and Polio Vaccine Contamination History

On November 30, 2018, an emergency committee on the global spread of polio, appointed by the World Health Organization, delivered its latest judgment: in 2017, cases caused by vaccine-derived viruses overtook, for the first time, those caused by the wild version.

Vaccine-derived polio virus (VDPV) is considered rare, but has become more noticeable since the wild virus itself has been all but eliminated (except in certain areas such as Afghanistan and Pakistan). Wild polio cases were declared eradicated in the U.S. in 1979 and eradicated in the western hemisphere in 1994. WHO has recommended “to eliminate the long-term risks of VDPV and vaccine-associated paralytic polio, for oral polio vaccines to be removed in a phased manner.” The first phase took place with the switch from trivalent to bivalent oral polio vaccine between April and May of 2016.

Polio is the common name for poliomyelitis, which comes from the Greek words for grey and marrow, referring to the spinal cord, and the suffix –itis, meaning inflammation. Poliomyelitis, shortened, became polio. For a time, polio was called infantile paralysis, though it did not affect only the young. Poliomyelitis is caused by a virus that multiplies in the gastrointestinal tract. There are three main serotypes of polio virus: PCV1, PCV2 and PCV3. Polio is transmitted when the virus enters the mouth or nose and infects the throat and gastrointestinal tract. In about 95% of cases, polio infection is subclinical and does not cause symptoms. In 4-5% of cases there may be minor symptoms, such as sore throat, low-grade fever, headache, fatigue and nausea followed by stiff neck, meningitis (brain inflammation) and temporary paralysis of an arm or leg, but there is full recovery within a few weeks. In less than 1% of cases, the polio virus infects the central nervous system and paralyzes the muscles of the arms and legs or muscles needed for breathing and swallowing, which can lead to permanent paralysis or death. Some adults, who appear to have fully recovered from polio as children, have developed post-polio syndrome and experience weakness and pain in muscles and joints.

Polio Vaccine

Two different kinds of polio vaccines have been given to children in the U.S. since the 1950’s and 1960’s: a live attenuated oral polio vaccine (OPV), which is no longer used in the U.S. (due to its potential of causing the disease), but is given to children in other parts of the world; and an inactivated, injectable polio vaccine (IPV), which has been given to children in the U.S. since 2000. Both live and inactivated polio vaccines contain PCV1, PCV2 and PCV3.

The live attenuated oral polio vaccine (OPV) can cause vaccine-derived polio in the vaccinated person or can cause vaccine-derived polio in a person who comes in contact with a recently vaccinated person’s body fluids (urine, stool, saliva) because the vaccine strain polio virus (VDPV) is shed for several weeks after vaccination. Vaccine-derived polio can cause mild or severe and permanent paralysis like the paralysis caused by wild type polio. VDPVs are classified as circulating (cVDPVs) when there is evidence of community transmission, or ambiguous (aVDPVs) when the identity is uncertain.

As of 1999, use of OPV was discontinued in the U.S. and replaced with inactivated, injectable polio vaccine, which can still cause adverse reactions, but cannot cause vaccine strain polio. However, OPV is still used widely in annual polio vaccine campaigns targeting children in parts of Asia, Africa and the Middle East. This is the form that the WHO is recommending eventually removing in a phase-out manner. Since 2000, more than 10 billion doses of OPV have been administered to nearly 3 billion children worldwide.

Since the type 2-component (PCV2) of trivalent OPV was considered most responsible for most cVDPV cases occurring after 2006, it was recommended that all countries cease using any type 2–containing OPV as of May 1, 2016. Hence, a globally synchronized switch from trivalent (tOPV) to bivalent OPV (bOPV, type 1- and 3-containing) occurred in all OPV-using countries. However, bivalent oral polio vaccine is still implicated as causing some reported vaccine-derived polio cases, and it is now confirmed in Papua New Guinea that VDPV1 is circulating and is being officially classified as a “circulating” VDPV type 1 (cVDPV1).

The reasons for still using the OPV instead of replacing it with the safer injectable polio vaccine (IVP) are primarily economic. First, OPV is cheap, costing only about 10 cents a dose versus $3 a dose for IVP. Second, it can be given as drops into a child’s mouth, which makes it far easier to administer than the injectable. Third, it is reported that there is not enough IVP on the market to vaccinate every child on the planet, and vaccine manufacturers claim they do not have the capacity to produce the quantities that would be needed if such a switch happened immediately. Hence, a recommended phase-out is the plan. Eradicating circulating vaccine-derived poliovirus (cVDPV) hinges on phasing out remaining oral poliovirus vaccine, which according to WHO, cannot be accomplished until wild polio is completely eradicated.

Hypogammaglobulinaemic vaccines can chronically excrete VDPV (iVDPV) for several decades. As long as OPV is used, cVDPV and iVDPV pose a risk of causing poliomyelitis and threaten the goal of poliovirus eradication. VDPV cannot arise from the inactivated poliovirus vaccine (IPV), but financial and logistical barriers to replace OPV with IPV remain.

In October 2018, VDPV has been reported in the Democratic Republic of the Congo, in the state of Borno in northeastern Nigeria, in several provinces in Papua New Guinea, in regions of Somalia, and in Syria. Genomic analysis of the strains involved showed that they had crossed borders, which is rare for vaccine-derived strains, and that some had circulated undetected for as long as four years. Health officials worry that the outbreaks may spread to neighboring countries. Despite response efforts (revaccination), transmission of these VDPVs has not yet been interrupted.

Vaccine Injury Compensation Program Statistics

As of September 1, 2015, 278 claims had been filed in the federal Vaccine Injury Compensation Program (VICP) for injuries and deaths following OPV-containing vaccines, including 14 deaths and 264 serious injuries. There had been 310 claims for injuries and deaths following IPV-containing vaccines, including 28 deaths and 282 serious injuries. Using the MedAlerts search engine, as of August 31, 2018 there had been 24,575 adverse events reported following OPV with 961 deaths (more than 90% in children under age six). There had been 40,633 reports of adverse events associated with IPV containing vaccines with 805 deaths (more than 90% in children under age six).

Marketed IVP and CDC Recommendations

There are four inactivated, injectable polio vaccines licensed and marketed in the U.S. by pharmaceutical companies. Three of the polio containing vaccines are combination vaccines that include additional vaccines to prevent other viral or bacterial infections.

In the U.S., the CDC recommends that infants and children receive a total of four doses of IPV with a dose at two and four months, between 6 and 18 months and between four and six years old.

Commonly reported IPV reactions include fever, irritability and crying, local reactions (pain, redness, swelling at injection site), drowsiness, vomiting and loss of appetite. However, because most IPV is included with other vaccines in combination shots in the U.S., the vaccine manufacturer product insert for each combination vaccine should be reviewed to learn about vaccine reaction symptoms and contraindications before vaccination.

The Dark History of Contaminated Polio Vaccines

It was in 1960 that an NIH scientist named Bernice Eddy discovered that rhesus monkey kidney cells used to make the Salk polio vaccine and experimental oral polio vaccines could cause cancer when injected into lab animals. Later that year, the cancer-causing virus in the rhesus monkey kidney cells was identified as SV40 or simian virus 40, SV40, which stands for “Simian Vacuolating Virus 40”, the 40th monkey virus to be discovered. Sadly, the American people were not told the truth about this in 1960. The SV40 contaminated stocks of Salk polio vaccine were never withdrawn from the market but continued to be given to American children until early 1963 with full knowledge of federal health agencies. Between 1955 and early 1963, nearly 100 million American children had been given polio vaccine contaminated with the monkey virus, SV40.

The presence of SV40 in monkey cell cultures used in the preparation of the polio vaccine from 1955 through 1961 is well documented. SV40 is a DNA tumor virus and, like other DNA tumor viruses, is not usually cancer causing in a natural host (such as rhesus monkeys) but becomes more oncogenic when it crosses species into other animals or humans. DNA tumor viruses also have an affinity for certain cell types. For example, human mesothelial (lung) cells appear to be particularly susceptible to malignant transformation in the presence of SV40.

After numerous studies showing SV40 was cancer-causing, weak regulations were put into place. Shockingly, the Division of Biologics Standards (DBS) of the National Institutes of Health (NIH) did not order a recall of any of the contaminated polio vaccines. They continued to distribute contaminated vaccines to an unsuspecting public until 1963. Finally, new federal regulations were put in place that required vaccines to be tested for SV40. These new regulations required a waiting period of 14 days to see if the virus was growing before making the vaccine. However, it was later discovered that a slower growing form of the virus, which took 19 days to appear, could have been in the approved vaccines. Therefore, millions more people worldwide potentially received contaminated vaccines all the way through the 1990s because of these inadequate testing guidelines.

Investigations have consistently demonstrated the oncogenic behavior of SV40 in animal models. Early epidemiological studies were inadequate in demonstrating an increase in cancer incidence associated with contaminated vaccines. Recently, investigators have provided persuasive evidence that SV40 is present in human ependymomas, choroid plexus tumors, bone tumors, and mesotheliomas, however, the etiologic role of the virus in tumorigenesis has not been established.

Today, U.S. federal health agencies admit the following two facts:

1. Salk polio vaccine released for public use between 1955 and 1963 was contaminated with SV40; and

2. SV40 has been proven to cause cancer in animals.

So why is it important today to find out whether the oral vaccine used to eradicate polio was in fact contaminated with a cancer-causing monkey virus, and that the vaccine manufacturer knew it, and that government health agencies looked the other way? It is important because if it is true, then a precedent has been set, and that precedent may well be affecting decisions being made by government health agencies today about what kinds of animal tissue cultures vaccine manufacturers will be allowed to use to make new vaccines and what kinds of tests will be required to insure that the vaccines do not contain animal viruses or other contaminants.


Balduzzi P, Glasgow LA. Paralytic poliomyelitis in a contact of a vaccinated child. New England Journal of Medicine 1967; 276:796-797.

Basillico FC, Bernat JL. Vaccine-associated poliomyelitis in a contact. Journal of the American Medical Association 1978; 239:2275.

Butel JS, Jafar S, Stewart AR, Lednicky JA. Detection of authentic SV40 DNA sequences in human brain and bone tumours. Dev Biol Stand 1998; 94: 23-32.

Carbone M, Pass HI, Miele L, Bocchetta M. New developments about the association of SV40 with human mesothelioma. Oncogene2003; 22: 5173-5180.

Cesario TC, Nakano JH, Caldwell GG, Youmans RA. Paralytic poliomyelitis in an unimmunized child: apparent result of a vaccine-derived poliovirus. American Journal of Diseases of Children 1969;118:895-898.

Cutrone r, Lednicky J, Dunn G et al. Some Oral Poliovirus Vaccines Were Contaminated with Infectious SV40 after 1961. Cancer Res2005; 65: 10273-10279.

Goedert J. Research on SV40 Exposure and the Development of Cancer. NIH Testimony: Subcommittee on Wellness and Human Rights, U.S. Committee on Government Reform. Sept. 10, 2003.

Institute of Medicine, National Academy of Sciences. 2002. Immunization Safety Review: SV40 Contamination of Polio Vaccine and Cancer. Washington, D.C.: National Academy Press.

Jorba J, Diop OM, Iber J, Sutter RW, Wassilak SG, Burns CC. Update on vaccine-derived polioviruses—worldwide, January 2015–May 2016. MMWR Morb Mortal Wkly Rep 2016;65:763–9. CrossRef PubMed.

Jorba J, Diop OM, Iber J, et al. Update on vaccine-derived polioviruses–worldwide, January 2016–June 2017. MMWR Morb Mortal Wkly Rep 2017;66:1185–91. CrossRef PubMed.

LaForce FM. Poliomyelitis vaccines: success and controversy. Infectious Disease Clinics of North America 1990;4:75-83.

Leake JP. Poliomyelitis following vaccination against this disease. Journal of the American Medical Association 1935;105:2152.

Lundstig A, Eliasson L, Lehtinen M et al. Prevalence and stability of human serum antibodies to simian virus 40 VP1 virus like particles. J Gen Virol 2005; 86(6): 1703-1708.

Martini F, Lazzarin L, Iaccheri L et al. Simian virus 40 footprints in normal human tissues, brain and bone tumors of different histotypes. Dev Biol Stand 1998; 94: 55-66.

Morse LJ, Rubin HE, Blount RE Jr. Vaccine-acquired paralytic poliomyelitis in an unvaccinated mother. Journal of the American Medical Association 1966;197:1034-1035.

National Vaccine Information Center MedAlerts.

Nkowane BM, Wassilak SG, Orenstein WA, Bart KJ, Schonberger LB, Hinman AR, et al. Vaccine-associated paralytic poliomyelitis, United States: 1973 through 1984. Journal of the American Medical Association 1987;257:1335-1340.

Openshaw H, Lieberman JS. Vaccine-related poliomyelitis: serum IgM and cerebrospinal fluid antibodies. Western Journal of Medicine 1983;138:420-422.

Riker JB, Brandt CD, Chandra R, Arrobio JO, Nakano JH. Vaccine-associated poliomyelitis in a child with thymic abnormality. Pediatrics 1971;48:923-929.

Wilson J, Robinson R. Poliomyelitis after contact with recently vaccinated infant (letter). British Medical Journal 1974;2:53.

World Health Organization Consultative Group. The relation between acute persisting spinal paralysis and poliomyelitis vaccine: results of a ten-year enquiry. Bulletin of the World Health Organization 1982;60:231-242.

Recent Posts