There are several reasons that society recommends vaccinations. The simplest reason is that vaccines prevent disease, and thus, society as a whole has fewer illnesses. The more individuals who are vaccinated against chickenpox, the fewer cases of chickenpox will occur. This means there will be fewer days missed from school and work and fewer visits to doctors and hospitals, thus increasing the productivity of society.
In addition, while some people may be only annoyingly ill from a disease, others might suffer severe complications from the same disease. For example, some cases of chickenpox are much more severe than others. Adolescents and adults with chickenpox are more likely to develop pneumonia and require hospitalization. If there are fewer cases of chickenpox in a community due to mass vaccination, then there will also be fewer severe cases of chickenpox in the community.
Let’s use a numerical example. If you have two million cases of chickenpox per year and one in every one thousand cases ends up in the hospital, you will have two thousand hospital admissions in a given year. However, if your vaccine decreases the number of cases by 95 percent (remember, no vaccine is perfect), then you will only have a hundred thousand cases of chickenpox and thus only a hundred hospital admissions. Immunizing society as a whole decreases the number of severe illnesses and hospitalizations associated with a disease.
Society also benefits from mass immunization because some individuals have medical reasons that prevent them from receiving a vaccine or that put them at a higher risk for complications if they get sick, such as having a suppressed immune system from chemotherapy. With fewer cases of chickenpox circulating in the community, there is a decreased risk that these immunosuppressed individuals will be exposed to the disease. This brings us to the concept of herd immunity.