Cardo 1997.

Methods	Cases and controls were selected and data on exposure and risk factors were collected retrospectively. Incident reports were reviewed to obtain information on case patients. Controls were reported to the CDC at the time of exposure and information was collected with a standardized protocol. Information about the health care worker, source patient, and injury were collected.
Participants	Cases: HCW who had documented occupational percutaneous exposure to HIV‐infected blood by a needlestick or a cut with a sharp object, HIV serovonversion temporally associated with the exposure and no other reported concurrent exposure to HIV. Controls: HCW with a documented occupational percutaneous exposure to HIV‐infected blood who were HIV seronegative at the time of exposure and at least six months later. All case patients reported in the USA by August 1994 who were exposed after 1987 and all controls exposed after 1987 whose six month follow‐up evaluation was completed as of August 1994 were studied. Case patients reported in France and Italy after 1989 and in the United Kingdom after 1987 were included. Thirty three cases and 679 controls were included in the study.
Interventions	Zidovudine post‐exposure prophylaxis was used. The majority of cases and controls took at least 1000 mg of zidovudine per day.
Outcomes	Risk factors for transmission of HIV
Notes	Setting: USA, France, Italy and United Kingdom