Behind glowing reports of the Salk polio vaccine’s success and even rosier predictions about the new, live, oral Sabin vaccine rages a storm of medical controversy that seldom reaches the ears of parents.
Many serious criticisms have been leveled at the Salk ‘ vaccine. These are now being acknowledged at least indirectly in announcements praising and promoting the new oral vaccines.
Yet all is not yet sweetness and accord among developers of the live, oral vaccines, either.
Evaluating the true effectiveness of the Salk vaccine and the new oral vaccines has been difficult for several reasons. Polio is a relatively rare disease in the United States. Because so few persons get it in its paralyzing form, success of an immunizing agent is hard to determine.
The definition of polio also has changed in the last six or seven years. Several diseases which were often diagnosed as polio are now classified as aseptic meningitis or illnesses caused by one of the Coxsackie or Echo viruses. The number of polio cases in 1961 cannot accurately be compared with those in, say 1952, because the criteria for diagnosis have changed.
Ever since the public was first informed about the Salk vaccine in the Francis report of April 12, 1955, the National Foundation has praised its effectiveness and urged parents to have themselves and their children vaccinated. Altho some physicians remained skeptical about the original theories behind the vaccine, about the techniques used in its evaluation, and about its success in combating polio, these objections seldom reached the general public. With the resurgence of paralytic polio in 1958 and 1959, the criticisms increased.
These views were summed up by five experts in a panel discussion on the “Present Status of Polio Vaccines” presented before the Illinois State Medical society in Chicago, in May, 1960, and published in the August and September issues of the Illinois Medical Journal. To make parents aware of the controversy about the Salk vaccine and the problems involved in developing an effective oral vaccine against polio, here is a report of that discussion:
Moderator of the panel was Herbert Ratner, M. D., director of public health in Oak Park, and associate clinical professor of preventive medicine and public health, Stritch School of Medicine, Chicago.
Dr. Ratner noted the upward trend in polio, particularly in the paralytic form, in the United States during 1958 and 1959. He quoted Dr. Alexander Lang-muir, in charge of polio surveillance for the United States public health service, as saying this resurgence is “cause for immediate concern.”
“In the fall of 1955, Dr. Langmuir had predicted that by 1957 there would be less than 100 cases of paralytic polio in the United States,” commented Dr. Ratner. “Four years and 300 million doses of Salk vaccine later, we had in 1959 approximately 6,000 cases of paralytic polio, 1,000 of which were in persons who had received three and more shots of Salk vaccine. Salk vaccine hasn’t lived up to expectations.”
Dr. Ratner next reviewed some basic facts about polio. Paralytic polio occurs in cycles and was in a natural decline when the Salk vaccine was introduced in 1955, he pointed out.
Prior to the introduction of the Salk vaccine, the National Foundation defined an epidemic as 20 or more cases of polio per year, per 100,000 population. Now, an epidemic is defined as 35 cases per year per 100,000. This change has resulted in a statistical — but not necessarily a real — drop in polio epidemics.
For every case of known paralytic polio, there are about a thousand ” subclinical polio infections,” so mild they pass unnoticed, Dr. Ratner explained. These mild cases account for the high degree of natural immunity in adults. You can have a polio infection in the intestines without having paralytic polio or nonparalytic polio with enough symptoms to be diagnosed.
Discussing the “very misleading way” in which the Salk vaccine data has been handled, was Bernard G. Greenberg, Ph. D., head of the department of bio-statistics of the University of North Carolina, school of public health, and former chairman of the committee on evaluation and standards of the American Public Health association.
“There has been a rise during the last two years in the incidence rates of paralytic poliomyelitis in the United States,” stressed Dr. Greenberg. “The rate in 1958 was about 50 per cent higher than that for 1957, and in 1959 about 80 per cent higher than that in 1958. If 1959 is compared with the low year of 1957, the increase is about 170 per cent.
“As a result of this trend in paralytic poliomyelitis, various officials in the public health service, official health agencies, and one large voluntary health organization have been utilizing the press, radio, and television and other media to sound an alarm bell in an heroic effort to persuade more Americans to take advantage of the vaccination procedures available to them,” said Dr. Greenberg.
“One of the most obvious pieces of misinformation being delivered to the American public is that the 50 per cent rise in paralytic poliomyelitis in 1958 and the real accelerated increase in 1959 have been caused by persons failing to be vaccinated. This represents a certain amount of double talk and an unwillingness to face facts and to evaluate the true effectiveness of the Salk vaccine,” said Dr. Greenberg.
The number of persons over 2 years of age in 1960 who have not been vaccinated cannot be more and must be considerably less than the number who had no vaccination in 1957, Dr. Greenberg pointed out. Then how can it be claimed that it is the large number of unvaccinated persons who are causing the increase in polio, when there were a larger number of unvaccinated individuals in 1957 when the vaccine was given credit for reducing rates of the disease.
“A scientific examination of the data and the manner in which the data was manipulated will reveal that the true effectiveness of the present Salk vaccine is unknown and greatly overrated,” Dr. Greenberg stressed.
Why was there such a tremendous reduction in reported rates of paralytic polio in 1955, 1956, and 1957? Much of this highly publicized decrease was a statistical illusion, said Dr. Greenberg.
Prior to 1954, any physician who reported a case of paralytic poliomyelitis was doing his patient a favor because funds were available to help pay his medical expenses. At that time, most health departments used a definition of paralytic poliomyelitis which specified “partial or complete paralysis of one or more muscle groups, detected on two examinations at least 24 hours apart.” Laboratory confirmation and the presence of residual paralysis were not required.
In 1955, these criteria were changed. Now, unless there is paralysis lasting at least 60 days after the onset of the disease, it is not diagnosed as paralytic polio.
During this period, too, “Coxsackie virus infections and aseptic meningitis have been distinguished from paralytic poliomyelitis,” explained Dr. Greenberg. “Prior to 1954, large numbers of these cases undoubtedly were mislabeled as paralytic polio.”
Thus, because the definition of the disease was changed and two similar diseases virtually ruled out, the number of cases of polio reported was sure to decrease in the 1955-57 period, vaccine or not. Then, too, physicians are reluctant today to diagnose paralytic poliomyelitis in a vaccinated child without thoro laboratory tests, thus eliminating most of the false positive cases commonly reported in the pre-1954 period.
“As a result of these changes in both diagnosis, and diagnostic methods, the rates of paralytic poliomyelitis plummeted from the early 1950s to a low in 1957,” said Dr. Greenberg.
The most accurate way we have of determining the effectiveness of vaccine (except by direct exposure to the disease) is to measure the levels of neutralizing antibodies in the blood, explained Herald R. Cox, Sc. D., director of virus research at Lederle Laboratories and president elect of the Society of American Bacteriologists. We do not know, he said, the exact level of antibodies necessary to protect against paralytic polio.
Herman Kleinman, M. D., an epidemiologist from the Minnesota department of health, pointed out that in antibody studies on children who have received three or more doses of Salk vaccine, he has found more than half do not have antibodies to two of the three types of polio strains used in the Salk vaccine. Twenty percent lack antibodies to a third type.
“This is a very disturbing fact,” said Dr. Kleinman. “If polio antibodies mean anything in respect to protection, then I am forced to conclude that much of the Salk vaccine we have been using is useless.”
Dr. Kleinman also commented on the “changing concept of polio” and said physicians were reluctant to diagnose the disease without overwhelming evidence. He called the insistence on a 60 day duration of paralysis in defining paralytic polio “silly.”
There have been problems, too, in the production of the killed Salk vaccine.
Mass vaccination with the Salk product started in April, 1955, and by April 26, there were reports of paralytic polio among vaccinated children, with deaths occurring in Idaho and California. Then came cases of polio among family members of vaccinated children. Live virus was discovered in the supposedly killed vaccine, altho it had been produced by the Salk procedure.
Other panel members agreed, pointing out that because all of the facts about the Salk vaccine have not been made public, physicians and public health officials find it difficult to resist the great pressures of public opinion built up thru an unprecedented publicity campaign urging the public to be vaccinated.
“Since nothing else is available, there seems to be no alternative but to push the use of it,” commented Dr. Greenberg.