Discussion Zoster incidence rate was higher in those with CKD and in those with CKD and diabetes mellitus compared to individuals without these conditions. Zoster VE in beneficiaries with CKD and with both CKD and diabetes mellitus was similar to VE in the overall study population (vaccine effectiveness 0.48 (95% CI, 0.39-0.56))[5] Medicare beneficiaries are reasonably representative of the older US population; 98% of Americans aged years were enrolled in Medicare in 2009.[11] Our study is large, giving power to assess VE in ≥65 individuals with CKD. Despite having adequate power to determine VE in the CKD cohort, our study size was insufficient to enable study of VE against PHN. Additionally, there were too few events amongst individuals on dialysis or with transplants to enable study of VE in these subgroups. VE was determined after adjusting for a wide range of confounders. Medicare is an administrative data source hence there could be misclassification of exposures and outcomes which may have led to a bias towards the null. Information on CKD stage was only available for 42% of individuals with CKD, hence it is not possible to comment on the VE of the zoster vaccine by CKD stage. Additionally, the study period was relatively short (maximum 2 years), due to data costs and availability issues, hence we could not determine vaccine effectiveness. Although the vaccine was licenced in 2006 and recommended by the Advisory Committee on Immunization Practices later that year, publication of the recommendation to vaccinate was delayed, which may have contributed to the low uptake of this vaccine. Uptake of the zoster vaccine remains low, but has gradually increased over time.[12] We have previously found that individuals with CKD were less likely to have received the zoster vaccine than people without CKD.[5] Previous studies have also reported increased incidence of zoster in adults with CKD and in those being treated with dialysis compared to those without CKD.[3, 4, 13] A recent retrospective cohort study from Taiwan reported a 27% increased zoster incidence in those with CKD
Discussion Zoster incidence rate was higher in those with CKD and in those with CKD and diabetes mellitus compared to individuals without these conditions. Zoster VE in beneficiaries with CKD and with both CKD and diabetes mellitus was similar to VE in the overall study population (vaccine effectiveness 0.48 (95% CI, 0.39-0.56))[5] Medicare beneficiaries are reasonably representative of the older US population; 98% of Americans aged ≥65 years were enrolled in Medicare in 2009.[11] Our study is large, giving power to assess VE in individuals with CKD. Despite having adequate power to determine VE in the CKD cohort, our study size was insufficient to enable study of VE against PHN. Additionally, there were too few events amongst individuals on dialysis or with transplants to enable study of VE in these subgroups. VE was determined after adjusting for a wide range of confounders. Medicare is an administrative data source hence there could be misclassification of exposures and outcomes which may have led to a bias towards the null. Information on CKD stage was only available for 42% of individuals with CKD, hence it is not possible to comment on the VE of the zoster vaccine by CKD stage. Additionally, the study period was relatively short (maximum 2 years), due to data costs and availability issues, hence we could not determine vaccine effectiveness. Although the vaccine was licenced in 2006 and recommended by the Advisory Committee on Immunization Practices later that year, publication of the recommendation to vaccinate was delayed, which may have contributed to the low uptake of this vaccine. Uptake of the zoster vaccine remains low, but has gradually increased over time.[12] We have previously found that individuals with CKD were less likely to have received the zoster vaccine than people without CKD.[5] Previous studies have also reported increased incidence of zoster in adults with CKD and in those being treated with dialysis compared to those without CKD.[3, 4, 13] A recent retrospective cohort study from Taiwan reported a 27% increased zoster incidence in those with CKD