Table 3

Meningococcal C vaccination effectiveness by periods of follow up. Catalonia, 1998–1999

Period of follow upVaccinated cohortUnvaccinated cohortVaccination effectiveness
UnadjustedAdjusted
Person yearsCasesPerson yearsCases%95% CI%95% CI
6 months347 4071289 267686−15,  988430, 97
12 months694 8141578 534119241, 999263, 98
18 months1 042 2212867 801179058, 989271, 98
24 months1 389 62821 157 068229268, 989478, 98