Table 1.

Counts and Percentages of Several Outbreak Parameters Among Two CCC Outbreaks of Varicella With High Coverage (H) and Low Coverage (L)

CCC H CCC L 
No. of children without history of varicella39 20
No. of children vaccinated (vaccination coverage in %)* 34 (87)6 (30)
No. (%) of cases 12 (31)12 (60)
No. (%) of cases among unvaccinated4 (80)12 (86)
No. (%) of cases among vaccinated8 (24)0 (0)
No. (%) of vaccinated among cases8 (67)0 (0)
% vaccine effectiveness (95% CI)71 (38–86)100 (67–100)
No. (%) of moderate-to-severe cases among unvaccinated children2 (40)6 (43)
No. (%) of moderate-to-severe cases among vaccinated children1 (3)0 (0)
% vaccine effectiveness for moderate-to-severe disease (95% CI)93 (33–99)100 (0–100)
Proportion of cases with moderate-to-severe disease among unvaccinated versus vaccinated in CCC H and CCC L combined (%)8/16 (50) vs. 1/8 (13)
Estimated no. of varicella cases that would have occurred if none of the children had been vaccinated (%)31 (80)17 (86)
Estimated no. (%) of moderate-to-severe varicella cases that would have occurred if none of the children had been vaccinated16 (40)9 (43)
  • * Proportions different between H and L; P < .001;

  • proportions different between H and L; P = .03.