5. Example - The measles, mumps and rubella (MMR) vaccine

The MMR vaccine is a combination vaccine against measles, mumps and rubella. Measles and mumps are highly contagious diseases with life-threatening complications, such as inflammation of the brain (encephalitis) and infection of the membranes that surround the brain and spinal cord (meningitis). Rubella infection results in a rash and cold-like symptoms. It is usually a mild disease, but in pregnant women it can harm the unborn baby, causing birth defects or even miscarriage. The MMR vaccine is given as a single injection into the muscle of the thigh or upper arm. It is a live-attenuated vaccine, so the vaccine contains weakened forms of each of the three disease-causing microorganisms. It is first given to babies at 12–13 months of age, with a booster due when children are between 3 and 5 years old. This provides long-term protection against the three diseases. The most common side effects are the development of very mild forms of measles and mumps that typically last for just a couple of days.

The MMR vaccine was introduced in the late 1980s and has radically reduced the number of cases of measles, mumps and rubella. Thanks to the vaccination programme, measles became extremely rare in Europe during the 1990s; however, a research paper published in 1998 suggesting a link between the MMR vaccine and autism resulted in vaccination rates falling in Europe. This research has since been entirely discredited because of false and unreliable results, but the fall in vaccination rates has led to several measles outbreaks across Europe. Catch-up vaccination programmes are now in place to increase the proportion of the population protected against these diseases.