Vaccine coverage: recent trends and future prospects.

OBJECTIVE--To assess the feasibility of achieving the target of 95% coverage for the childhood immunisation schedule by 1995 and to determine the influence of sociodemographic factors and information systems on recent trends. DESIGN--Analyses of trends in quarterly vaccination data for diphtheria, pertussis, and measles in health districts between February 1988 and February 1991. SETTING--District health authorities in England and Wales, and health and social services boards in Northern Ireland. SUBJECTS--Cohorts of children whose youngest member had reached the target age of 18 months for receiving the third doses of diphtheria and pertussis vaccines and 2 years for receiving measles vaccine. RESULTS--Predicted coverage levels for mid-1995 were in excess of 95% for diphtheria, pertussis, and measles vaccines. In the 118 districts that continuously reported between February 1988 and February 1991 the increase in coverage was 6% for diphtheria and 13% for pertussis and measles vaccines. 1991 coverage depended primarily on 1988 coverage. The additional effects of deprivation, change in computer system, and child population size achieved at most only marginal statistical significance. CONCLUSIONS--The government''s target of 95% coverage by 1995 is realistic, although projections should be viewed with caution. Several national vaccination initiatives are likely to have contributed to the recent steady increase in coverage. Updating and validation exercises are likely to improve recorded coverage.