Table 2.

Analysis of age at first exposure to an influenza season in a study of leukemia risk among California children diagnosed between 1997 and 2007

All cases and controlsFirst birthsSecond or subsequent births
Controls (n = 31,460)Cases (n = 1,573)ORa (95% CI)Controls (n = 12,226)Cases (n = 585)ORa (95% CI)Controls (n = 19,222)Cases (n = 988)ORa (95% CI)
All ALL cases combined
Age at first exposure to influenza season, mo
0–39,792455Ref3,814163Ref5,973292Ref
3–68,0184161.12 (0.97–1.28)3,1511531.14 (0.91–1.42)4,8642631.11 (0.93–1.31)
6–97,5433801.08 (0.94–1.25)2,8961301.05 (0.83–1.33)4,6452501.10 (0.93–1.31)
9–125,4442941.16 (1.00–1.35)2,0871281.44 (1.13–1.82)3,3551661.01 (0.83–1.23)
>12663280.91 (0.62–1.34)278110.93 (0.50–1.73)385170.90 (0.55–1.49)
  • aORs adjusted for birth year.