Vaccines: An overview and update

Vaccines prevent death on a large scale, but only if enough people are immunised. If most of the people within a population are vaccinated against an infection, those who are not will still be protected because spread of the pathogen is blocked. This is known as “herd immunity”. However, this immunity relies on public support of vaccination programmes which, in turn, strongly depends on perception of risk versus benefit. For example, the controversy relating to the safety of the combined measles, mumps and rubella (MMR) vaccine stemming from proposed links with autism has had a detrimental impact on the protection of children from these diseases within the UK. While most of the researchers who initially proposed this link subsequently retracted their speculations, the damage in terms of public confidence was done. A marked reduction in the percentage of the population immunised against MMR (from 92 to 82 per cent) occurred across the UK, with some areas of London reporting an uptake 20 per cent lower than the national average.1 The World Health Organization recommends an immunity level of 95 per cent to prevent disease outbreaks. The reduction in MMR vaccinations has been reflected by increased reports of measles and mumps in the UK and, in response, some health authorities are holding publicity events and training primary care staff to encourage uptake of the combined vaccine.