Table 1

Age-specific incidence (cases per thousand) of varicella and trends, Massachusetts, 1998–2003
Year
 Parameter
 Age group in years




< 1
 1–4
 5–9
 10–14
 15–19
 20+
 All ages, crude
1998








na
 144
 762
 1025
 922
 791
 8241
 11885

Cases
 4
 66
 83
 23
 9
 34
 219

Incidence
 15.2
 82.6
 76.4
 18.6
 30.2
 2.2
 16.5

95% CI
 4.7–49.5
 59.9–113.9
 55.0–104.5
 10.8–32.0
 8.3–109.4
 1.4–3.5
 12.8–21.3









1999








na
 318
 1603
 1131
 1094
 898
 8483
 13527

Cases
 4
 46
 41
 11
 3
 17
 122

Incidence
 6.2
 36.5
 38.2
 10.4
 2.9
 1.7
 10.9

95% CI
 1.2–31.6
 21.1–63.0
 24.8–59.0
 4.8–22.5
 0.6–13.4
 0.9–3.4
 7.8–15.1









2000








na
 139
 671
 790
 918
 693
 7518
 10729

Cases
 1
 7
 9
 9
 3
 3
 32

Incidence
 11.4
 11.6
 10.3
 8.8
 4.2
 0.3
 2.7

95% CI
 1.4–53.7
 4.7–25.6
 4.8–20.6
 4.0–18.1
 0.8–19.8
 0.1–1.23
 1.8–4.3









2002








na
 161
 600
 780
 831
 705
 7789
 10866

Cases
 1
 4
 5
 3
 1
 6
 20

Incidence
 8.7
 4.3
 8.0
 4.6
 1.4
 0.5
 1.7

95% CI
 1.1–44.6
 1.2–13.9
 3.0–20.0
 1.3–15.4
 0.2–9.7
 0.2–1.1
 1.0–2.8









2003








na
 155
 613
 827
 914
 726
 8012
 11247

Cases
 0
 7
 15
 6
 2
 10
 40

Incidence
 0.0
 8.8
 15.0
 6.4
 2.3
 1.6
 3.5

95% CI
3.6–20.2
 7.8–27.0
 2.7–14.4
 0.6–9.2
 0.8–3.1
 2.3–5.2









1998–2003








% change for period
 -100%
 -89%
 -80%
 -66%
 -92%
 -27%
 -79%

p for trend test
 n.a.
 <0.0001
 <0.0001
 0.02
 0.15
 0.16
 <0.0001

a N's exclude individuals for whom age or varicella status was missing. The number excluded for these reasons was 494, 233, 478, and 195 in 1999, 2000, 2002, and 2003, respectively. Values for n's and numbers of cases are unweighted, whereas incidence rates and 95% confidence intervals are based on weighted analysis.

Yih et al. BMC Public Health 2005 5:68   doi:10.1186/1471-2458-5-68