Between 1990 and 2015, under-5 mortality rate (U5MR) declined by 53%, from an estimated rate of 91 deaths per 1000 live births to 43, globally. The aim of this study was to determine the share of health research systems in this decrease alongside other influential factors.We used random effect regression models including the 'random intercept' and 'random intercept and random slope' models to analyze the panel data from 1990 to 2010. We selected the countries with U5MRs falling between the first and third quartiles in 1990. We used both the total articles (TA) and the number of child-specific articles (CSA) as a proxy of the health research system. In order to account for the impact of other factors, measles vaccination coverage (MVC) (as a proxy of health system performance), gross domestic product (GDP), human development index (HDI), and corruption perception index (CPI) (as proxies of development), were embedded in the model.Among all the models, 'the random intercept and random slope models' had lower residuals. The same variables of CSA, HDI, and time were significant and the coefficient of CSA was estimated at -0.17; meaning, with the addition of every 100 CSA, the rate of U5MR decreased by 17 per 1000 live births.Although the number of CSA has contributed to the reduction of U5MR, the amount of its contribution is negligible compared to the countries' development. We recommend entering different types of researches into the model separately in future research and including the variable of 'exchange between knowledge generator and user.'