By A. G. Moore
The following is adapted from the Rhythm Prism publication Jonas Salk. Although Jonas Salk was written with young readers in mind, there’s a lot in the book that may be informative to more mature readers. For example, until I researched this book, I didn’t understand why the Salk or Sabin vaccine would be used in specific circumstances. Now I do understand: each vaccine has different risks and benefits
Adaptation from Jonas Salk:
Both the oral and injectable forms of the polio vaccine have been in use for more than fifty years. This has given the global community enough experience to understand risks and benefits of each.
Since the Sabin vaccine uses a live, though weakened virus, there is a slight chance that vaccination will actually give someone polio. This has happened in a small number of cases. Because of this risk, the Sabin vaccine was discontinued in the US and only the Salk is administered.
However, there is also a risk from the Salk vaccine. With the Salk vaccine, a very weak immunity is produced in the gut. If someone who has been vaccinated is exposed to wild polio, there is the possibility that the wild virus will multiply in the gut. Though the vaccinated individual may not become ill with polio, they can shed virus in their excrement. This shed virus then becomes a source of contagion for others in the community.
Because of the way the Sabin and Salk vaccines work, they are generally used in different places. If there is good vaccine coverage in an area, and most people have immunity to polio, then the Salk vaccine is used. This is generally considered safer because the vaccine cannot make the individual sick, and virus shed in excrement will not be dangerous to others who have been vaccinated.
On the other hand, if a polio vaccination campaign is conducted in an area where there are many unvaccinated people, the oral vaccine might be considered preferable. With the oral vaccine there is no risk of shed virus infecting unvaccinated people. However, the risk remains that in a small number of cases, someone may actually contract polio from the vaccine itself. Not only can these people become ill, but they can infect others who haven’t been vaccinated.
One more consideration in the selection of vaccines is cost. Giving the Salk vaccine is about five times more expensive than giving the Sabin vaccine. In areas where resources are scarce, this is an important factor.