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Updated: Jul 14, 2026

Inverse Probability of Treatment Weighting (Propensity Score) using the Military Health System Data Repository and National Death Index
Published on: January 8, 2020
Concurrent vaccinations and U.S. military hospitalizations
Daniel C Payne1, Aaron Aranas, Michael M McNeil
1Bacterial Vaccine-Preventable Disease Branch, Epidemiology and Surveillance Division, National Immunization Program, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. dvp6@cdc.gov
Purpose:
To investigate whether concurrent vaccinations (> or =2 vaccinations on consecutive days) are associated with hospitalization risk among U.S. military personnel.
Methods:
We analyzed Defense Medical Surveillance System data from January 1998 through December 2003 for 117,876 active component U.S. military personnel. We performed a time-to-event analysis of a historical cohort using a Cox proportional hazards model comparing hospitalizations during a 120-day postvaccination exposure interval to hospitalizations within a 120-day pre-exposure interval. We excluded personnel who were deployed during these intervals and those having hospitalizations 60 days prior to the concurrent vaccination exposure. Hazards ratios (HRs) with 95% confidence intervals were calculated, adjusting for demographic, occupational, health, and calendar variables.
Results:
We analyzed 19,743 persons having concurrent vaccinations. Receiving two or more vaccinations concurrently was not statistically associated with the adjusted risk of hospitalization (HR = 0.90 [0.75, 1.09]). Furthermore, no statistically significant associations were detected for 3 concurrent vaccinations (HR = 0.86 [0.58, 1.28]), 4 concurrent vaccinations (HR = 1.08, [0.66, 1.74]), or five or more concurrent vaccinations (HR = 0.86 [0.49, 1.51]).
Conclusions:
No evidence was found that the concurrent receipt of multiple vaccinations is related to hospitalization risk among this sample of U.S. military personnel.
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