3.8

• Placebo


  A 'dummy' treatment with no medical or therapeutic value. A placebo looks like the drug being tested but only contains sugar
• Standard deviation


  An important measure of spread or dispersion. It tells us how far on average the results are from the mean
• Vaccine


  Substances containing disabled antigens of a particular disease, usually administered via injection. Vaccines stimulate the body to produce antibodies to provide immunity against that disease
• All vaccines and drugs are tested using clinical trials before being licenced for use
• The purpose of clinical trials is to allows drugs to be checked for: Safety, Effectiveness, Dosage
• Design of clinical trials to test vaccines and drugs

  1. Randomised

  2. Placebo-controlled

  3. Double-blind
• Randomised


  Subjects in clinical trials are divided into groups in a randomised way to reduce bias in the distribution of characteristics such as age and gender
• Placebo-controlled


  One group of participants will be given the drug and another control group will be given the placebo. It is important that participants are not aware of which group they are in. Following the completion of the trial, results will be compared
• Double-blind


  Neither the subjects nor the researchers know which group subjects are in to prevent biased interpretation of the results. One group of subjects receives the vaccine or drug while the second group receives a placebo control to ensure valid comparison
• Researchers must ensure that the subject groups are of a suitable size to reduce the magnitude of experimental error
• A small subject group increases the chance that an unknown factor could affect the result. It is less likely to pick up on variation between individuals
• The subject groups need to be of a large enough size in order to have some relevance when applying the data to the wider population
• It is important that subject groups have sufficient diversity so that the results of the trial reflect the population and avoid bias. Care needs to be taken to properly reflect age, gender, ethnicity, class and geographic spread
• The results from all groups are compared to determine whether there are any statistically significant differences between the groups
• Results of clinical trials are displayed as a graph and often feature error bars. Error bars are used to determine significant differences between mean results
• Small error bar


  Smaller deviation from the mean value
• Larger error bar


  Wider spread of data from the mean value