Vaccine trial stages that collect information continuously on vaccine usage, adverse effects, and long-term immunity. Vaccine trials may take months or years to complete, since a sufficient time period must elapse for the subjects to react to the vaccine and develop the required antibodies. Poliomyelitis, a viral disease, has the potential to damage the central nervous system and leave children paralyzed. Jonas Salk developed an attenuated vaccine to combat the rising prevalence of the disease around the world. In 1955 the results from the preliminary trial of Salk’s vaccine were announced to the general public and within 2 hours it was licensed.
Jonas Salk "I had an opportunity to spend time in elective periods in my last year in medical school, in a laboratory that was involved in studies on influenza. The influenza virus had just been discovered about a few years before that. And, I saw the opportunity at that time to test the question as to whether we could destroy the virus infectivity and still immunize. And so, by carefully designed experiments, we found it was possible to do so." In 1941, during his postgraduate work in virology, Salk chose a two-month elective to work in the laboratory of Thomas Francis at