Polio

Prior to 1954 any physician who reported paralytic poliomyelitis [Polio] was doing his patient a service by way of subsidizing the cost of hospitalization and was being community-minded in reporting a communicable disease. The criterion of diagnosis at that time in most health departments followed the World Health Organization definition: “Spinal paralytic poliomyelitis: Signs and symptoms of nonparalytic poliomyelitis with the addition of partial or complete paralysis of one or more muscle groups, detected on two examinations at least 24 hours apart.”

Note that “two examinations at least 24 hours apart” was all that was required. Laboratory confirmation and presence of residual paralysis was not required. In 1955 the criteria were changed to conform more closely to the definition used in the 1954 field trials: residual paralysis was determined 10 to 20 days after onset of illness and again 50 to 70 days after onset. The influence of the field trials is still evident in most health departments; unless there is residual involvement at least 60 days after onset, a case of poliomyelitis is not considered paralytic.

This change in definition meant that in 1955 we started reporting a new disease, namely, paralytic poliomyelitis with a longer lasting paralysis. Furthermore, diagnostic procedures have continued to be refined. Coxsackie virus infections and aseptic meningitis have been distinguished from paralytic poliomyelitis. Prior to 1954 large numbers of these cases undoubtedly were mislabeled as paralytic poliomyelitis. Thus, simply by changes in diagnostic criteria, the number of paralytic cases was predetermined to decrease in 1955–1957, whether or not any vaccine was used. At the same time, the number of nonparalytic cases was bound to increase because any case of poliomyelitis-like disease which could not be classified as paralytic poliomyelitis according to the new criteria was classified as nonparalytic poliomyelitis. Many of these cases, although reported as such, were not nonparalytic poliomyelitis. If this inaccurate number of cases of nonparalytic poliomyelitis reported in 1957 is accepted as accurate and considered as a base for subsequent comparisons, it is no wonder that we now say nonparalytic cases went down in 1958.

There is still another reason for the decrease in the reported paralytic poliomyelitis cases in 1955–1957. As a result of the publicity given the Salk vaccine, the public questioned the possibility of a vaccinated child developing paralytic poliomyelitis. Whenever such an event occurred, every effort was made to ascertain whether or not the disease was truly paralytic poliomyelitis. In fact, I am certain that many health officers and physicians here will ask routinely if a child has been vaccinated when signs of poliomyelitis are present during the summer months. We have been conditioned today to screen out false positive cases in a way that was not even imagined prior to 1957.

As a result of these changes in both diagnosis and diagnostic methods, the rates of paralytic poliomyelitis plummeted from the early 1950’s to a low in 1957.

DDT (dichloro-diphenyl-trichloroethane) was developed as the first of the modern synthetic insecticides in the 1940s. It was initially used with great effect to combat malaria, typhus, and the other insect-borne human diseases among both military and civilian populations. It also was effective for insect control in crop and livestock production, institutions, homes, and gardens. DDT’s quick success as a pesticide and broad use in the United States and other countries led to the development of resistance by many insect pest species.

Regulation Due to Health and Environmental Effects

The U.S. Department of Agriculture, the federal agency with responsibility for regulating pesticides before the formation of the U.S. Environmental Protection Agency in 1970, began regulatory actions in the late 1950s and 1960s to prohibit many of DDT’s uses because of mounting evidence of the pesticide’s declining benefits and environmental and toxicological effects.

• SV40 is a virus found in some species of monkey.
• SV40 was discovered in 1960. Soon afterward, the virus was found in polio vaccine.
• More than 98 million Americans received one or more doses of polio vaccine from 1955 to 1963 when a proportion of vaccine was contaminated with SV40; it has been estimated that 10–30 million Americans could have received an SV40 contaminated dose of vaccine.
• SV40 virus has been found in certain types of cancer in humans, but it has not been determined that SV40 causes these cancers.
• The majority of scientific evidence suggests that SV40-contaminated vaccine did not cause cancer; however, some research results are conflicting and more studies are needed.
• Polio vaccines being used today do not contain SV40. All of the current evidence indicates that polio vaccines have been free of SV40 since 1963.

In 1960, it was discovered that Simian Virus 40 (SV40) contaminated up to 30% of the poliovirus vaccines in the US. This contamination arose because the vaccines were produced in monkey kidney cell cultures harboring SV40 between 1955 and 1963. During this period, approximately 90% of children and 60% of adults in the USA were inoculated for polio and possibly exposed to SV40. Many epidemiologic and molecular pathogenesis studies have been conducted in order to identify potential cancer risks since this ‘natural’ experiment began. Productive SV40 infection has the potential to initiate malignancy in a variety of target tissues. Epidemiological studies that investigated the relationship between SV40 infection and cancer risks have yielded mixed results.

Simian virus 40 (SV40) is a small DNA tumor virus of monkey origin. This polyomavirus was administered to human populations mainly through contaminated polio vaccines, which were produced in naturally infected SV40 monkey cells. Previous molecular biology and recent immunological assays have indicated that SV40 is spreading in human populations, independently from earlier SV40-contaminated vaccines. SV40 DNA sequences have been detected at a higher prevalence in specific human cancer specimens, such as the brain and bone tumors, malignant pleural mesotheliomas, and lymphoproliferative disorders, compared to the corresponding normal tissues/specimens. However, other investigations, which reported negative data, did not confirm an association between SV40 and human tumors.

In 1955, some batches of polio vaccine given to the public contained live polio virus, even though they had passed required safety testing. Over 250 cases of polio were attributed to vaccines produced by one company: Cutter Laboratories. This case, which came to be known as the Cutter Incident, resulted in many cases of paralysis. The vaccine was recalled as soon as cases of polio were detected.

[According to CDC data, the Cutter Incident resulted in 164 cases of paralysis and 10 deaths.]

Although the incidence of polio acute flaccid paralysis (AFP) has decreased in India, the nonpolio AFP (NPAFP) rate has increased. Nationwide, the NPAFP rate is 11.82 per 100 000 population, whereas the expected rate is 1 to 2 per 100 000 population. We examined the correlates of NPAFP to discern explanations for the increase. The incidence of polio AFP in India has decreased. However, the nonpolio AFP rate has increased since 2000. Follow-up of these cases of nonpolio AFP is not done routinely. However, one-fifth of these cases of nonpolio AFP in the state of Uttar Pradesh (UP) were followed up after 60 days in 2005; 35.2% of patients were found to have residual paralysis, and 8.5% had died. This suggests that the pathology in children being registered as having nonpolio AFP cannot be considered trivial. Therefore, there is a compelling reason to try to determine the underlying causes for the surge in nonpolio paralysis numbers.

[…]

NPAFP increased with the number of oral polio vaccine (OPV) doses used (R2 = 25.02%; P < .001). When effect of cumulative doses over the previous years was examined, the NPAFP rate in 2013 best correlated with the cumulative doses received in the previous 7 years (R2 = 57.16%), with 2012 excluded because data for this year were incomplete. This correlation was highly significant (P < .001). On multiple regression analysis, the number of OPV doses was the only factor that showed a positive correlation with the NPAFP rate.

On 9 August 2020, the Federal Ministry of Health, Sudan notified WHO of the detection of a circulating vaccine-derived poliovirus type 2 (cVDPV2) in the country. According to the notification, the virus is genetically-linked with Chad (sequencing results showed 12 to 19 nucleotide changes). Two Acute Flaccid Paralysis (AFP) cases were notified.