Herd immunity

• Vaccinations allow protection against specific diseases, but the level of protection depends on the amount of people vaccinated.
• Some diseases can be treated with antibiotics.
• Herd immunity is the protection given to a population against an outbreak of a specific disease when a very high percentage of the population have been vaccinated against it.
• There are three recognised scenarios in relation to herd immunity: The majority of the population are not vaccinated against a specific disease, however, a few people are ill and contagious.
• Most of the population are not vaccinated against the specific disease but are well, some are vaccinated and healthy, and a few are not vaccinated, but ill and contagious.
• Mass infection can result again, but a small number of vaccinated individuals remain healthy and some that are not vaccinated will also be healthy.
• The majority of the population are vaccinated and healthy against a specific disease, a few are not vaccinated but well.
• A few are not vaccinated against the disease, and they are ill and contagious.
• A few individuals will still become ill, but the large number of vaccinated individuals gives protection.
• The measles vaccine was introduced in 1968 which caused a sharp decline to approximately 150,000 cases in 1969.
• Clear fluctuations are detected until approximately 1964.
• A new MMR (measles, mumps, and rubella) vaccine was introduced in 1988, which caused a further sharp decline in recorded cases from approximately 50 cases per thousand.
• The majority of individuals are protected due to high levels of vaccination.
• 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.
• This increases the number of infections, as well as the number of people who could die from a specific infectious disease.
• 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.
• In 1950 approximately 380,000 cases of measles were detected, indicating that measles were regularly detected at approximately 600,000 cases per year in 1952, with some reductions to approximately 150,000 cases in 1954.