Impact of Chief Medical Officer activity on prescribing of antibiotics in England: an interrupted time series analysis

Background Antimicrobial resistance is a growing problem, with the need for strong action' highlighted by the Chief Medical Officer for England in 2013, along with a 5year antimicrobial resistance strategy. Objectives Five years on, we set out to determine if there was a measurable impact from the 5year antimicrobial resistance strategy on overall antibiotic prescribing in NHS primary care in England. Methods We calculated the volume of antibiotic prescription items using annual prescription cost analysis data from 1998 to 2017 and monthly prescribing data from October 2010 to June 2018. Antibiotic prescribing rate was calculated using an age- and sex-adjusted denominator (Specific Therapeutic group Age-sex Related Prescribing Units, STAR-PU). We conducted interrupted time series analysis to measure any change in prescribing rate after the intervention. Results After several years with a stable rate of antibiotic prescribing, there was a downward change in gradient after 2013: -46.4 items per 1000STAR-PU per year (95% CI=-61.4 to -31.3). The prescribing rate dropped from 1378 per 1000STAR-PU per year in 2013 to 1184 in 2017, representing a 14.1% reduction. The reduction is similar for monthly data (16.4%). Assuming causality, when compared with predicted prescribing if the rate of prescribing had continued at the pre-2013 trend, we estimate that 9.7 million antibiotic prescriptions were prevented over the past year by the 5year antimicrobial resistance strategy. Conclusions Though we cannot firmly attribute causality for the reduction in prescribing to the 5year antimicrobial resistance strategy, the magnitude and timing of the change are noteworthy; the substantial change followed a long period of relatively static antibiotic prescribing.