Live Vaccine Against Measles, Mumps, and Rubella and the Risk of Hospital Admissions for Nontargeted Infections

IMPORTANCE In low-income countries, live measles vaccine reduces mortality from causes other than measles infection. Such nonspecific effects of vaccines might also be important for the health of children in high-income settings. OBJECTIVE To examine whether the live vaccine against measles, mumps, and rubella (MMR) is associated with lower rates of hospital admissions for infections among children in Denmark. DESIGN, SETTING, AND PARTICIPANTS Population-based cohort study of Danish children born 1997-2006 and followed up from ages 11 months to 2 years (last follow-up, August 31, 2008). Nationwide Danish registers provided data on vaccinations and hospital admissions. The recommended vaccination schedule was inactivated vaccine against diphtheria, tetanus, pertussis, polio, and Haemophilus influenzae type b (DTaP-IPV-Hib) administered at ages 3, 5, and 12 months and MMR at age 15 months. MAIN OUTCOMES AND MEASURES Incidence rate ratios (IRRs) of hospital admissions for any infection, comparing receipt of MMR vs DTaP-IPV-Hib as the most recent vaccine. Risks, risk difference, and number needed to vaccinate were calculated for receiving MMR on time. RESULTS The study included 495 987 children contributing with 56 889 hospital admissions for any type of infection during 509 427 person-years (rate, 11.2 per 100 person-years). Receiving the live MMR vaccine after the inactivated DTaP-IPV-Hib-vaccine was associated with a lower rate of hospital admissions for any infection. [GRAPHICS] The risk of admission for an infection between ages 16 months and 24 months was 4.6% (95% CI, 4.5%-4.7%) for receiving MMR on time and 5.1% (95% CI, 5.0%-5.2%) for not receiving MMR on time. The risk difference was 0.5 percentage point (95% CI, 0.4-0.6), and the number needed to vaccinate with MMR before age 16 months to prevent 1 infectious disease admission was 201 (95% CI, 159-272). CONCLUSIONS AND RELEVANCE In a cohort of Danish children, receipt of live MMR vs inactivated DTaP-IPV-Hib as the most recent vaccine was associated with a lower rate of hospital admissions for any infections. These findings require replication in other high-income populations.