TABLE 4.

Prevalence ratio (PR) for nasopharyngeal pneumococcal colonization among urban children by time from penicillin use to study enrollment — Alaska, 2000–2010 (n=3,496)^*

Children using penicillin	Non-Colonized PR (95% CI)	PCN-S Colonized PR (95% CI)	PCN-NS Colonized PR (95% CI)
None ≤90 prior to enrollment	Reference	Reference	Reference
≤ 30 days prior to enrollment	1.37 (1.29–1.44)	0.32 (0.24–0.43)	0.84 (0.64–1.11)
31–60 days prior to enrollment	1.07 (0.97–1.18)	0.62 (0.47–0.80)	1.50 (1.16–1.95)
61–90 days prior to enrollment	1.11 (1.00–1.24)	0.79 (0.61–1.02)	1.03 (0.73–1.45)

Abbreviations: PCN-NS, full, plus intermediate penicillin resistance (MIC > 0.064 mcg/mL); PCN-S, penicillin susceptible (MIC ≤ 0.064 mcg/mL)

^*PR adjusted for age, sex, day-care attendance, and 7-valent pneumococcal vaccination status