Following a vaccination, a person becomes immune to the specific disease. This immunity gives protection against illness in an individual. The majority of the population must be vaccinated against serious diseases, this can reduce the chance of people coming into contact with specific pathogens before they are able to be vaccinated and protects the vulnerable in society. It is called herd immunity.
There are three recognised scenarios in relation to herd immunity and they are described below.
If the number of people vaccinated against a specific disease drops in a population, it leaves the rest of the population at risk of mass infection, as they are more likely to come across people who are infected and contagious. This increases the number of infections, as well as the number of people who could die from a specific infectious disease.
Describe the incidence of measles before and after the measles vaccine was introduced in 1968.
In 1950 approximately 380 000 cases of measles were detected. This shows that measles were regularly detected at approximately 600 000 cases per year in 1952, with some reductions to approximately 150 000 cases in 1954. Clear fluctuations are detected until approximately 1964. The measles vaccine was introduced in 1968 which caused a sharp decline to approximately 150 000 cases in 1969.
Explain how the introduction of the new MMR vaccine affected the cases of measles recorded.
A new MMR (measles, mumps and rubella) vaccine was introduced in 1988, which caused a further sharp decline in recorded cases. In 1994 the Measles / Rubella campaign was introduced and then a second dose of MMR vaccination was introduced in 1996, which resulted in cases falling to almost 0 cases in 2004.