Disease Detectives Called in to Solve Polio Scare

Almost five decades have passed since the nationwide testing of the Salk polio vaccine. The largest medical experiment in history, its legacy is seen in current efforts to eradicate the world of this infectious viral disease that causes permanent paralysis. It was just five decades ago that parents in the United States were afraid to allow their children to go to a swimming pool or sandbox for fear the virus would confine them to a wheelchair.

Neal Nathanson, a medical resident from the University of Chicago and newly named EIS officer in 1955, vividly recalls the time. "The trial went from the spring of 1954 to the fall of that year. It wasn't until April 1955 that all the data were analyzed, which concluded that the Salk vaccine was 60 to 90% effective."

Five selected manufacturers, including the Cutter Laboratory in California, had already prepared the vaccine for widespread use in anticipation of a successful field trial. The FDA approved the vaccine, and children across the nation soon eagerly lined up to receive the vaccine in the spring of 1955. By the end of April, public euphoria over the vaccine's effectiveness came to a crashing halt when several cases of child paralysis occurred, causing a public panic and raising doubts over the vaccine's safety. On May 8, the U.S. Surgeon General suspended the entire U.S. vaccine program pending inspection of each manufacturer's production plant.

"People began to question that if this product was unsafe, how do we know that every other vaccine is safe? The credibility of the Public Health Service was also on the line," recalls Nathanson. It was essential to solve the polio cases before parents lost faith in the vaccines that protected their children from DTP (diphtheria, tetanus, pertussis) and other devastating diseases.

Overnight, CDC's chief epidemiologist, Alexander D. Langmuir, M.D., M.P.H., set up the Polio Surveillance Unit to investigate the outbreak. He staffed the unit with a secretary and two EIS officers, including Nathanson, one of the few EIS officers never to have taken a formal EIS training course. Instead, he received on-the-job mentoring in the science of epidemiology from Dr. Langmuir himself.

The surveillance unit began gathering data from state health departments around the country, which received reports from local health departments on every case of polio reported. There was very little 'natural' polio occurring during that time of the year.

The public was anxious for information so CDC issued daily reports of its investigation. The New York Times printed the reports on its front page for a month, underscoring the national attention that the outbreak received.

"It became clear that these cases were associated with a couple of states – California and Idaho. Further investigation revealed that the source was from two lots of vaccine from a single manufacturer – the Cutter lab," Nathanson recalls.

With the cause of the outbreak isolated by the EIS, the FDA quickly lifted its moratorium on the vaccine with the other manufacturers beginning on May 13.

CDC reviewed 260 polio cases, including 94 recipients of the Cutter vaccine, 126 family members who were infected from close contact with the children, and another 40 community contacts.

The quick work of the EIS under Dr. Langmuir's direction helped allay fears, rescue the vaccine program, and restore public confidence in the vaccine and the U.S. Public Health Service. At the same time, the outbreak pointed to the need for a national disease surveillance capability. Today, CDC works with its partners to conduct surveillance for hundreds of diseases and conditions, such as AIDS, Lyme disease, lead poisoning, tobacco use, work-related injuries, birth defects, and cancer.

The EIS' findings also led the Federal government to establish more stringent standards for manufacturing vaccines and for testing the safety of products in general. Specifically, before a vaccine is licensed, manufacturers must provide a full production history and a consistent positive outcome on product safety testing.

The United States has not seen a new case of polio since 1979. Thanks to a global eradication effort spearheaded by CDC, the World Health Organization, Rotary International, and UNICEF, polio is limited to just 20 countries and is due to be eradicated by 2002.

"I feel very lucky – it was happenstance that I was drawn into this," says Nathanson of his EIS work with the Polio Surveillance Unit. Nathanson went on to serve as head of infectious diseases at Johns Hopkins Medical School, and in 1995 he retired from the University of Pennsylvania Medical Center after 17 years. Nathanson also just finished two and a half years as director of the Office of AIDS Research at NIH, where he is credited with "bringing a public health perspective to the organization."

Although the Salk vaccine is well-regarded as the first step toward the elimination of polio, the pioneering investigative work of the EIS and the Polio Surveillance Unit ensured the vaccine's survival at a critical point in its young history. At the same time, the work of Dr. Langmuir, Nathanson, and others fueled the creation of a nationwide disease surveillance capability by CDC that continues to flourish today.