Poster presented at the 36th Annual International Society for Pharmacoepidemiology Conference
Objective: The objective of this study was to identify the most appropriate comparator group for a cohort study assessing safety outcomes in recipients of the two-dose adjuvanted Recombinant Zoster Vaccine (RZV) in recipients aged ≥ 50 years.
Results: A total of 261,050 individuals received at least one dose of RZV during the study period. Of these, 133,256 individuals received the recommended two doses during the study period. The number of individuals with at least one comparator visit ranged from 1,666,326 to 6,698,184, depending on the definition used. The mean age for each of the comparator groups was similar to that of RZV recipients (68 years, standard deviation: 9 years). Adults unexposed to RZV who received a routine annual physical exam or an age-appropriate preventive screening measure were comparable based on descriptive comparisons to RZV recipients.
Conclusions: There were substantive differences in the prevalence of some comorbidities when comparing characteristics of RZV recipients to those of individuals in six different potential comparator groups of unexposed individuals. These differences highlight the importance of the rigorous selection of a comparator group in cohort studies evaluating vaccine effectiveness or safety, especially in older adults who have multiple comorbidities. By evaluating six different comparator group definitions, we identified an algorithm that would select unexposed individuals comparable to RZV recipients in this cohort study.
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