Herd immunity
Following a vaccination, a person can become immune to the specific Illness affecting plants and animals.. This When a person's body is not prone to a disease because they have a resistance to it. gives protection against illness in an individual. The majority of the population must be vaccinated against serious diseases, which can reduce the chance of people coming into contact with specific Microorganism that causes disease., leading to 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. This can develop easily into a mass infection because the majority of the population are not vaccinated.
- 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. The result is that the majority are protected due to the high level of vaccination. A few individuals will still become ill, but the large number of vaccinated individuals gives protection.
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.
Question
Describe, using the data, the pattern before and after the measles vaccine was introduced in 1968.
In 1950 approximately 380,000 cases of measles were detected. The rate increased and decreased until the vaccine was introduced in 1968. Some years had rates as low as 150, 000 and others were more than 600, 000. After the measles vaccine was introduced in 1968 there was a sharp decline to approximately 150, 000 cases in 1969. The rate increased and decreased a little after this but remained on an overall decline.
Question
Describe, using data, the effect of the introduction of the MMR vaccine on the number of measles cases recorded.
A new MMR (measles, mumps and rubella) vaccine was introduced in 1988, which caused a further sharp decline in recorded cases from approximately 50, 000. In 1994 a second vaccine for measles (the Measles / Rubella campaign) was introduced. Shortly afterwards a second dose of MMR vaccination was introduced in 1996, which resulted in cases falling to the low thousands.
Question
Describe, using the data, the effectiveness of vaccines in the percentage reduction of cases.
The whooping cough vaccination in 1957 reduced the total number of cases from 92,407 to 9. This is a percentage reduction of 99.99%. The measles vaccination in 1968 reduced the total number of cases from 460,407 to 53. This is also a percentage reduction of 99.99%. These are the most significant percentage reductions.
The 1942 diphtheria vaccination reduction was next highest at 99.83% followed by 1999 group C invasive meningococcal diseases at 89.81%. The 2006 invasive pneumococcal disease vaccination percentage reduction was 63.88% and lowest was the 1992 Haemophilus influenza type b at 29.47%.
