Polio vaccine (Salk)

The invention: Jonas Salk’s vaccine was the first that prevented polio,resulting in the virtual eradication of crippling polio epidemics.The people behind the invention:

Jonas Edward Salk (1914-1995), an American physician,

immunologist, and virologist

Thomas Francis, Jr. (1900-1969), an

American microbiologist

Cause for Celebration

Poliomyelitis (polio) is an infectious disease that can adversely

affect the central nervous system, causing paralysis and great muscle

wasting due to the destruction of motor neurons (nerve cells) in

the spinal cord. Epidemiologists believe that polio has existed since

ancient times, and evidence of its presence in Egypt, circa 1400 b.c.e.,

has been presented. Fortunately, the Salk vaccine and the later vaccine

developed by the American virologist Albert Bruce Sabin can

prevent the disease. Consequently, except in underdeveloped nations,

polio is rare. Moreover, although once a person develops polio,

there is still no cure for it, a large number of polio cases end without

paralysis or any observable effect.

Polio is often called “infantile paralysis.” This results from the

fact that it is seen most often in children. It is caused by a virus and

begins with body aches, a stiff neck, and other symptoms that are

very similar to those of a severe case of influenza. In some cases,

within two weeks after its onset, the course of polio begins to lead to

muscle wasting and paralysis.

On April 12, 1955, the world was thrilled with the announcement

that Jonas Edward Salk’s poliomyelitis vaccine could prevent the

disease. It was reported that schools were closed in celebration of

this event. Salk, the son of a New York City garment worker, has

since become one of the most well-known and publicly venerated

medical scientists in the world.

Vaccination is a method of disease prevention by immunization,

whereby a small amount of virus is injected into the body to prevent

a viral disease. The process depends on the production of antibodies

(body proteins that are specifically coded to prevent the disease

spread by the virus) in response to the vaccination. Vaccines are

made of weakened or killed virus preparations.

Electrifying Results

The Salk vaccine was produced in two steps. First, polio viruses

were grown in monkey kidney tissue cultures. These polio viruses

were then killed by treatment with the right amount of formaldehyde

to produce an effective vaccine. The killed-virus polio vaccine

was found to be safe and to cause the production of antibodies

against the disease, a sign that it should prevent polio.

In early 1952, Salk tested a prototype vaccine against Type I polio virus

on children who were afflicted with the disease and were thus

deemed safe from reinfection. This test showed that the vaccination greatly elevated the concentration of polio antibodies in these children.

On July 2, 1952, encouraged by these results, Salk vaccinated fortythree

children who had never had polio with vaccines against each of

the three virus types (Type I, Type II, and Type III). All inoculated children

produced high levels of polio antibodies, and none of them developed

the disease. Consequently, the vaccine appeared to be both safe in

humans and likely to become an effective public health tool.

In 1953, Salk reported these findings in the Journal of the American

Medical Association. In April, 1954, nationwide testing of the Salk

vaccine began, via the mass vaccination of American schoolchildren.

The results of the trial were electrifying. The vaccine was safe,

and it greatly reduced the incidence of the disease. In fact, it was estimated

that Salk’s vaccine gave schoolchildren 60 to 90 percent protection

against polio.

Salk was instantly praised. Then, however, several cases of polio

occurred as a consequence of the vaccine. Its use was immediately

suspended by the U.S. surgeon general, pending a complete examination.

Soon, it was evident that all the cases of vaccine-derived polio

were attributable to faulty batches of vaccine made by one

pharmaceutical company. Salk and his associates were in no way responsible

for the problem. Appropriate steps were taken to ensure

that such an error would not be repeated, and the Salk vaccine was

again released for use by the public.

Consequences

The first reports on the polio epidemic in the United States had

occurred on June 27, 1916, when one hundred residents of Brooklyn,

New York, were afflicted. Soon, the disease had spread. By August,

twenty-seven thousand people had developed polio. Nearly seven

thousand afflicted people died, and many survivors of the epidemic

were permanently paralyzed to varying extents. In New York City

alone, nine thousand people developed polio and two thousand

died. Chaos reigned as large numbers of terrified people attempted

to leave and were turned back by police. Smaller polio epidemics

occurred throughout the nation in the years that followed (for example,

the Catawba County, North Carolina, epidemic of 1944). A

particularly horrible aspect of polio was the fact that more than 70 percent of polio victims were small children. Adults caught it too;

the most famous of these adult polio victims was U.S. President

Franklin D. Roosevelt. There was no cure for the disease. The best

available treatment was physical therapy.

As of August, 1955, more than four million polio vaccines had

been given. The Salk vaccine appeared to work very well. There were

only half as many reported cases of polio in 1956 as there had been in

1955. It appeared that polio was being conquered. By 1957, the number

of cases reported nationwide had fallen below six thousand.

Thus, in two years, its incidence had dropped by about 80 percent.

This was very exciting, and soon other countries clamored for the

vaccine. By 1959, ninety other countries had been supplied with the

Salk vaccine.Worldwide, the disease was being eradicated. The introduction

of an oral polio vaccine by Albert Bruce Sabin supported

this progress.

Salk received many honors, including honorary degrees from

American and foreign universities, the LaskerAward, a Congressional

Medal for Distinguished Civilian Service, and membership in

the French Legion of Honor, yet he received neither the Nobel Prize

nor membership in the American National Academy of Sciences. It

is believed by many that this neglect was a result of the personal antagonism

of some of the members of the scientific community who

strongly disagreed with his theories of viral inactivation.