RISK-FACTORS FOR PERTUSSIS IN YOUNG INFANTS DURING AN OUTBREAK IN CHICAGO IN 1993

Because young infants are at highest risk for severe pertussis and dea th and are also too young to have received the minimal protective seri es of three doses of diphtheria-tetanus-pertussis (DTP) vaccine, we co nducted a matched case-control study to assess risk factors for pertus sis among young infants during a pertussis outbreak in Chicago in 1993 . We enrolled 39 cases <7 months of age from a single teaching hospita l and 96 controls, individually matched for age, from the well-child c linic at the same hospital. Demographic characteristics, immunization status, and opportunities for disease exposure were analyzed by means of conditional logistic regression. Cases and controls were similarly up to date with their DTP vaccinations (87% and 89%, respectively). In fants of adolescent mothers (matched odds ratio [OR], 6.4; 95% confide nce interval [CI], 1.3-41.4) and infants of mothers who suffered great er than or equal to 7 days of cough during the child's incubation peri od (matched OR, 12.0; 95% CI, 1.4 to infinity) were significantly more likely to have pertussis, Young mothers and mothers with a cough last ing greater than or equal to 7 days may be an important source of pert ussis infection for their young infants.