Sourced from https://www.youtube.com/watch?v=cEn1PKyBUNc 7.41am 6/10/20

Herd immunity occurs when the vaccination of a significant portion of a population (or herd) provides a measure of protection for individuals who have not developed immunity. The percentage of the population vaccinated in order to achieve herd immunity depends on the disease.

When a high percentage of the population is protected, through vaccination, against a virus or bacteria, it is difficult for a disease to spread through the population because as there are so few susceptible people left to infect.

This can slow or effectively stop the spread of the disease in the population. It is particularly crucial for protecting people who cannot be vaccinated for one reason or another. Not all people can be vaccinated, these include children who are too young to be vaccinated, people with immune system problems, and those who are too ill to receive vaccines (such as some cancer patients).

The video above helps to explain how herd immunity works and what happens when herd immunity breaks down.

Measles is an extremely contagious viral infection and is more serious than people may think. Measles develops complications that include, ear infections, pneumonia or diarrhoea. However in January 2015 a measles outbreak in Disneyland brought the spot light on citizens who refuse to vaccinate themselves or their children, thus reducing the herd immunisation rates to dangerous levels.

Measles is quite an underestimated viral infection. Just like the cold virus it is spread through sneezing or coughing. People with a weakened immune system are particularly at risk, for example, people who are receiving cancer treatment in the form of chemotherapy or radiotherapy. People who take high doses of steroid medication are extremely vulnerable as are pregnant women who are not immunised exposing themselves to high risks of miscarriage. People who are infected don't necessarily know they are infected and can spread the virus 4 days before they show symptoms of infection.

1) What is "Herd Immunity"?

2) What groups of people benefit from herd immunity?

3) Herd immunity breaks down when the number of people vaccinated falls. Explain why.

Consider the article written in the Guardian.

1) Why was Disneyland an ideal place for such a viral outbreak?

2) Explain how such an outbreak can occur using the term "Herd Immunity"

3) People say "It's my body so its my choice to be vaccinated". Argue against this view.