Dr. Hanley

1. Please comment on the Salk vaccine Vs. the Sabin vaccine.

The Salk vaccine uses killed polio virus, and was the first one used in mass vaccination campaigns. It was administered by injection. The Salk vaccine was then replaced by the Sabin vaccine, which contained live but attenuated polio virus, and was given by mouth. The Sabin vaccine however carried a higher risk of producing polio and spreading it to others. Recently, in places where the risk of an unvaccinated person getting polio is now very low, and the risk of getting polio from the Sabin vaccine may exceed this low risk, some authorities have switched back to the less risky Salk vaccine. It is a question of balancing risks and benefits.

2. At what point does a “problem” become an epidemic and when do Epidemiologists become involved?

A good example is the Norwalk virus on cruise ships. The cruise companies have infection control policies that escalate control efforts as daily counts rise. Public health authorities on land have similar policies. These policies work well for diseases they have previously dealt with and know well. But when a new disease emerges, they have to rely on principles they have developed with diseases they know better. For example, the response to the H1N1 threat, and the targeting of high risk groups, borrowed in part from developing knowledge, but also from knowledge of how the Spanish Flu acted. Of course, it may emerge later that the new disease acts somewhat differently than what was considered its closest cousin.
We need to distinguish the epidemiology scientists, many of them working in laboratories, from the epidemiology (public health) practitioners. The scientists work out the nature of the disease process and how it spreads, and the practitioners are guided by this knowledge.Hi Jennifer,