However the bias due to the healthy vaccinee effect is largely cancelled out by taking the ratio of relative incidence in two subgroups
(M and F) where Palbociclib the healthy vaccinee effect manifests similarly. We calculated excess events per 100,000 vaccinated using the following approach described in more detail elsewhere [17]: For one group: equation(A) Events per 100,000 exposures=100,000Nexposed/RI−1/RI×Eriskwhere Nexposed is the number of vaccinated individuals, RI is the relative incidence of events in risk versus control periods, and Erisk is the number of events in the risk period. To compare excess risk among two groups: When the excess risk is compared across two groups a common baseline risk must be assumed. This is achieved by pooling the total exposures and pooling the total events in the control group and rearranging the relative incidence expression. equation(B) Events per 100,000 males=100,000Nexposed(M+F)/(RIM−1)×Econtrol(M+F) 5FU equation(C) Events per 100,000 females=100,000Nexposed(M+F)/(RIF−1)×Econtrol(M+F)where Nexposed(M+F) is the total in both groups who were vaccinated, RIF and RIM are the sex-specific relative incidence estimates and Econtrol(M+F) is the number of events in the control
period for males plus females. The excess number of events in females compared to males is simply the difference of the two excess event calculations: (C) – (B). We conducted several sensitivity analyses to evaluate the robustness of our conclusions. We examined the impact of vaccination on the incidence of ER visits and admissions separately. For the 12-month vaccination, we compared the relative incidence in a pre-vaccination period from −30 to −8 days before vaccination about compared to our original 20–28 days post-vaccination
control period. We also compared the age at the time of receipt of the 12-month vaccination for males and females. We conducted our 12-month analysis for the period of April 1st 2002 to March 31st 2004 (before the introduction of the Men-C vaccine) to evaluate whether the effect we observed was independent of the addition of this vaccine to the recommended schedule. Furthermore, we conducted a restricted analysis which eliminated diagnoses that were unlikely to be secondary to vaccine reactions. Our analysis included data on children born between April 1, 2002 and December 31, 2009. For the combined analysis of 2-, 4- and 6-month vaccinations, data were available for 1866,136 vaccinations in 703,156 unique children. For our analysis of the 12-month vaccination, data was available for 548,422 vaccinated children. For vaccinations at 2, 4 and 6 months combined, the relative incidence of events (95% CI) in the first 72 h after vaccination as compared to the control period was 0.69 (0.67 to 0.71).