Christine L. Case, Ed.D.
Biology Professor
Skyline College

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Relative Risk Example

Risk Factors for Meningococcal Disease in College Students
From: JAMA. 2001;286(6):688-693)

These data are from a one-year case-control study of college students conducted by the CDC. The study used questionnaires to calculate rates and risks of disease across a wide range of demographic and behavioral variables. Controls were matched to cases by college attended, age, and sex. A total of 96 cases of meningococcal bacteremia or meningitis were identified. There was winter predominance, with 46% of cases occurring between December and March; and rates were highest in the northern and southeastern parts of the country.

 

Meningococcal disease

No meningococcal disease

 

Dormitory

(a) 95

(b) 305

e=a/(a+b)

Not in dorm

(c) 21

(d) 279

f=c/(c+d)

Relative risk = e/f = 3.39

Notes: Meningococci are Neisseria meningitis. Approximately 5% to 10% of the general population carries the meningococcal bacteria in the nose and throat in a harmless state. This carrier state may last for days or months and seems to give those individuals who harbor meningococci in their upper respiratory tract some protection from actually developing the disease state

This report provides compelling evidence in support of the recommendations of the Advisory Committee on Immunization Practices (ACIP) to advise college students of the risk and immunization opportunity for meningococcal disease. More pointedly, it would seem that the risk for a specific subset of college students, freshmen living in dormitories, is sufficiently high to make a stronger recommendation for that group.