Table 3– Risk of death from invasive pneumococcal pneumonia in each month compared with July–September by age group and Charlson comorbidity score during 1994–2007

Age years	Month	Die n	Survive n	Case fatality %	Risk ratio (95% CI)
40–64
Low comorbidity (Charlson 0)	November	9	84	9.7	1.0 (0.5–2.0)
	December	27	177	13.2	1.4 (0.9–2.2)
	January	16	150	9.6	1.0 (0.6–1.7)
	February	12	166	6.7	0.7 (0.4–1.3)
	March	11	196	5.3	0.6 (0.3–1.1)
	April–October	55	529	9.4	Reference
Medium/high comorbidity (Charlson ≥1)	November	10	64	13.5	0.8 (0.4–1.4)
	December	18	112	13.9	0.8 (0.5–1.3)
	January	21	75	21.9	1.2 (0.8–1.9)
	February	22	102	17.7	1.0 (0.6–1.7)
	March	11	117	8.6	0.7 (0.4–1.3)
	April–October	81	381	17.5	Reference
≥65
Low comorbidity (Charlson 0)	November	19	132	12.6	1.1 (0.7–1.8)
	December	42	235	15.2	1.4 (0.9–1.9)
	January	34	144	19.1	1.7 (1.2–2.5)^#
	February	32	178	15.2	1.4 (0.9–2.0)
	March	30	169	15.1	1.3 (0.9–2.0)
	April–October	68	540	11.2	Reference
Medium/high comorbidity (Charlson ≥1)	November	45	203	18.2	0.9 (0.7–1.2)
	December	129	328	28.2	1.4 (1.1–1.6)^#
	January	68	225	23.2	1.1 (0.9–1.4)
	February	84	227	27.0	1.3 (1.1–1.6)^#
	March	69	238	22.5	1.1 (0.9–1.4)
	April–October				Reference

^#: 95% confidence interval does not include 0 (significant at p<0.05).