Immunisation and MMR

health science

: Case Scenario 1: Immunisation and MMR

The case scenario

In Finland in the 1970’s the mean annual incidence of measles was 366 per 100,000 people; the incidence of mumps was 240 per 100,000 and rubella was 104 per100,000 people. At the time, the population of Finland was 5 million people, and large epidemics of measles, mumps and rubella caused hundreds of hospitalisationseach year.

Live-virus vaccinations for measles and rubella were introduced in 1975, but because only 70% of the target population was vaccinated, this did not result inelimination of these diseases. In 1982 a combined live-virus measles-mumps-rubella (MMR) vaccine was approved, and a large voluntary and free immunisation programcommenced.

The immunisation program consisted of two vaccine doses of 0.5mL each that was injected under the skin in either the upper arm or buttocks, by public health nursesat community child health centres. Children were vaccinated at age 14 – 18 months and again when six years of age. Not all parents chose to have their childrenimmunised with the free MMR vaccination, despite widespread publicity about the program.

At one child health clinic in a rural region of Finland, 130 children aged 14-18 months presented for routine health care. The parent/guardian of 87 of thesechildren agreed to have their child vaccinated with the MMR vaccine as part of this free program.

A group of Finnish public health researchers monitored all the children aged 14-18 months at the clinic, including those who were immunised and those who were not.They noted any adverse reactions to the vaccine among children who were vaccinated, and they determined the incidence of measles in the children in the following12 months.

There were some vaccine-related complications among vaccine recipients across the country. There were no deaths or long term disability among any childrenattributed to the vaccine. Small numbers of children were noted to have elevated temperature beyond the normal childhood range (34.7 -37.3 °C) in the seven daysfollowing immunisation. Approximately 7 in 100,000 children experienced febrile convulsions and five children (0.6 in 100,000) had hives as an allergic reaction tothe vaccine. Twenty three children (3.3 cases in 100,000 vaccinated children) developed acute thrombocytopenic purpure (a bleeding condition where the blood doesnot clot as it normally should).

Q2. Please read the case scenario carefully. What research design have the researchers used and what level of evidence does it present? What information isprovided in the case scenario about the characteristics of the research design to support your answer?