Risk of Nontargeted Infectious Disease Hospitalizations Among US Children Following Inactivated and Live Vaccines, 2005-2014.

Background: Recent studies have shown that some vaccines have beneficial effects that cannot be explained solely by the prevention of their respective targeted disease(s).

Methods: We used the MarketScan US Commercial Claims Databases for 2005 to 2014 to assess the risk of hospital admission for nontargeted infectious (NTI) diseases in children aged 16 through 24 months according to the last vaccine type (live and/or inactivated). We included children continuously enrolled within a month of birth through 15 months who received at least 3 doses of diphtheria-tetanus-acellular pertussis vaccine by the end of 15 months of age. We used Cox regression to estimate hazard ratios (HRs), stratifying by birthdate to control for age, year, and seasonality and adjusting for sex, chronic diseases, prior hospitalizations, number of outpatient visits, region of residence, urban/rural area of domicile, prematurity, low birth weight, and mother's age.

Results: 311663 children were included. In adjusted analyses, risk of hospitalization for NTI from ages 16 through 24 months was reduced for those who received live vaccine alone compared with inactivated alone or concurrent live and inactivated vaccines (HR, 0.50; 95% confidence interval [CI], 0.43, 0.57 and HR, 0.78; 95% CI, 0.67, 0.91, respectively) and for those who received live and inactivated vaccines concurrently compared with inactivated-only (HR, 0.64; 95% CI, 0.58, 0.70).

Conclusions: We found lower risk of NTI disease hospitalizations from age 16 through 24 months among children whose last vaccine received was live compared with inactivated vaccine, as well as concurrent receipt compared with inactivated vaccine.