Differences in risk factors for partial and no immunisation in the first year of life: prospective cohort study BMJ Volume 332, pp 1312-13

The mothers of children who are unimmunised differ from those who are partially immunised in a number of ways, finds a study in this week’s BMJ.

This is the first large scale study of its kind in the UK, and suggests that different approaches are needed to maximise uptake of immunisation in these groups.

Researchers from the Institute of Child Health analysed data for 18,488 infants born between September 2000 and January 2002 in the UK. The sample was stratified by UK country and electoral wards to adequately represent infants from ethnic minority groups and disadvantaged backgrounds.

Mothers were interviewed when the infants were about 9 months old. They were shown a card listing the primary vaccines, given at 2, 3, and 4 months of age, and asked if the infants had received three doses of all listed vaccines.

Overall, 3.3% of infants were partially immunised and 1.1% were unimmunised. These rates were highest in England (3.6% and 1.3% respectively).

Partially immunised infants were more likely to come from an ethnic minority group, a disadvantaged background, and a large family. They were also more likely to have a teenaged or lone parent, a mother who smoked during pregnancy, and have been admitted to hospital at least once.

In contrast, unimmunised infants were more likely to have older (40 years or above) and more highly qualified mothers, or mothers of black Caribbean ethnicity.

Mothers cited medical factors relating to their child or family as the predominant reason for partial immunisation. Mothers’ beliefs or attitudes towards immunisation were the main reason cited for no immunisation.

These findings indicate that mothers of unimmunised and partially immunised infants differ in terms of age and education, say the authors. “Our study suggests that different interventions are needed to promote uptake of immunisation among older and more highly qualified mothers who reject primary immunisations,” they conclude.