Take this reportВ ofВ a Measles virus outbreak on the island of Majuro. To calculate the relative risk of lung cancer to the smoking group we simply divide their risk of disease (10%) by that of the non-smoking group (2.5%) which gives us a Relative Risk of 10/ 2.5= 4, or to put it another way, the smoking group had four times the risk of lung cancer of the non-smoking group.В IвЂ™ve illustrated this example below, which might be easier to visualise: Risk ratios can also be calculated in studies of vaccine effectiveness. Although an equal number of people from each group came down with lung cancer, 15/ 600 non-smokers or 2.5% of that group got the disease, compared to 15/ 150 or 10% of the smokers. As an example, imagine an office block of workers, containing 600 non-smokers and 150 smokers, and after ten years thirty of the people have lung cancer:В 15 smokers and 15 non-smokers. Relative risk (also known as вЂrisk ratioвЂ™ or RR) is the more intuitive of the two measures, and is calculated relatively simply.

This data is used to calculate вЂRelative RiskвЂ™ and вЂVaccine EfficacyвЂ™ values as a way of quantifying the effects of the intervention on the disease.

Groups of people either given the vaccine or not are followed, and researchers record whether or not they catch the disease in question. So, is this a validВ point? On what basis are vaccines even considered to be effective, and how does that determination hold up against data from actual outbreaks in which the immunised can represent the majority of cases? Vaccines are evaluated for effectiveness in preventing disease in much the same way as any other intervention on a disease outcome. While the media seem to be pushing the line that the unvaccinated are responsible for bringing these diseases back, when you look at the numbers from, in fact most of the cases of the disease were in people who received the vaccine! В Clearly this vaccine isnвЂ™t working if theВ vaccinated make up most of the notifications. If you follow the social media postings of various anti-vaccination groups, youвЂ™ve probably seen them point to contemporary outbreaks of disease, and say something along the lines of:

Serial cloner leaving out a nucleotide