Intended for healthcare professionals


Protective effect of antibiotics against serious complications of common respiratory tract infections: retrospective cohort study with the UK General Practice Research Database

BMJ 2007; 335 doi: (Published 08 November 2007) Cite this as: BMJ 2007;335:982
  1. I Petersen, statistician1,
  2. A M Johnson, head of department1,
  3. A Islam, database manager1,
  4. G Duckworth, consultant epidemiologist2,
  5. D M Livermore, microbiologist2,
  6. A C Hayward, senior lecturer infectious disease epidemiology1
  1. 1UCL Centre for Infectious Disease Epidemiology, Department of Primary Care and Population Sciences, University College London, London NW3 2PQ
  2. 2Health Protection Agency, Centre for Infections, London NW9 5EQ
  1. Correspondence to: A Hayward a.hayward{at}
  • Accepted 13 August 2007


Objective To determine the extent to which antibiotics reduce the risk of serious complications after common respiratory tract infections.

Design Retrospective cohort study.

Setting UK primary care practices contributing to the general practice research database.

Data source 3.36 million episodes of respiratory tract infection.

Main outcome measures Risk of serious complications in treated and untreated patients in the month after diagnosis: mastoiditis after otitis media, quinsy after sore throat, and pneumonia after upper respiratory tract infection and chest infection. Number of patients needed to treat to prevent one complication.

Results Serious complications were rare after upper respiratory tract infections, sore throat, and otitis media, and the number needed to treat was over 4000. The risk of pneumonia after chest infection was high, particularly in elderly people, and was substantially reduced by antibiotic use, with a number needed to treat of 39 for those aged ≥65 and 96-119 in younger age groups.

Conclusion Antibiotics are not justified to reduce the risk of serious complications for upper respiratory tract infection, sore throat, or otitis media. Antibiotics substantially reduce the risk of pneumonia after chest infection, particularly in elderly people in whom the risk is highest.


  • Contributors: ACH was chief investigator, had the original idea for the study, and developed the analytical strategy with IP. The study plan was refined with input from all authors. IP analysed the data. AI extracted the relevant data from the database. IP and ACH drafted the paper, incorporating comments from the other authors. ACH is guarantor.

  • Funding: Department of Health.

  • Competing interests: DML has various shareholdings and grants from pharmaceutical companies. AMJ has undertaken brief consultancy for GlaxoSmithKline in HPV epidemiology.

  • Ethical approval: GPRD scientific and ethical advisory committee.

    Provenance and peer review: Not commissioned; externally peer reviewed.

  • Accepted 13 August 2007
View Full Text