Biology - AQA - Unit 2 - C3. Immunity and Vaccines

1. Natural - this is when you become immune after catching a disease.

2. Artificial - this is when you become immune after you’ve been given a vaccination exposing you to a harmless dose of antigen

This is the type of immunity you get from being given antibodies made by a different organism - your immune system doesn’t produce any antibodies of its own

Exam Tip
Don’t get active and passive immunity mixed up in the exam. Just remember that in active immunity your body is actively doing something-it’s producing antibodies.

While your B-cells are busy dividing to build up their numbers to deal with a pathogen (i.e. the primary response), you suffer from the disease. Vaccination can help avoid this.
Antigens in vaccines cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease. This means you can become immune without getting any symptoms. Vaccines protect individuals that have them and, because they reduce the occurrence of the disease, those not vaccinated are also less likely to catch the disease (because there are fewer people to catch it from). This is called herd immunity

Vaccines usually contain antigens - these may be free or attached to a dead or attenuated (weakened) pathogen. Vaccines may be injected or taken orally. The disadvantages of taking a vaccine orally are that it could be broken down by enzymes in the gut or the molecules of the vaccine may be too large to be absorbed into the blood. Sometimes booster vaccines are given later on (e.g. after several years) to make sure that more memory cells are produced.

• All vaccines are tested on animals before being tested on humans-some people disagree with animal testing. Also, animal based substances may be used to produce a vaccine, which some people disagree with.

• Testing vaccines on humans can be risky, e.g. volunteers may put themselves at unnecessary risk of contracting the disease because they think they’re fully protected (e.g. they might have unprotected sex because they have had a new
  HIV vaccine and think they’re protected—and the vaccine might not work).

• Some people don’t want to take the vaccine due to the risk of side effects, but they are still protected because of herd immunity-other people think this is unfair.

• If there was an epidemic of a new disease (e.g. a new influenza virus) there would be a rush to receive a vaccine and difficult decisions would have to be made about who would be the first to receive it.