Although randomized placebo-controlled trials (RCT) are critical to establish efficacy of vaccines at the time of licensure, important remaining questions about vaccine effectiveness (VE) -used here to include individual-level measures and population-wide impact of vaccine programs --can only be answered once the vaccine is in use, from observational studies. However, such studies are inherently at risk for bias. Using a causal framework and illustrating with examples we review newer approaches to detecting and avoiding confounding and selection bias in three major classes of observational study design: cohort, case-control, and ecological studies. Studies of influenza VE, especially in seniors, are an excellent demonstration of the challenges of detecting and reducing such bias, and so we use influenza VE as a running example. We take a fresh look at the time-trend studies often dismissed as "ecological." Such designs are the only observational study design that can measure the overall effect of a vaccination program (indirect (herd) as well as direct effects), and are in fact already an important part of the evidence base for several vaccines currently in use. Despite the great strides towards more robust observational study designs, challenges lie ahead for evaluating best practices for achieving robust unbiased results from observational studies. This is critical for evaluation of national and global vaccine program effectiveness.

IMPORTANCE Atopic dermatitis (AD) is a highly prevalent condition that may be associated with an altered gastrointestinal microbiota that promotes an immune environment more susceptible to allergic disease. Synbiotics, a mixture of prebiotics and probiotics, have been used for the prevention and treatment of AD. OBJECTIVE To investigate the efficacy of synbiotics for primary prevention and treatment of AD.

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The use of social media as a powerful health communication tool is an area of current research interest. Our objective was to describe use of Facebook by State Health Departments (SHDs) in US, and their relationship with CDC's Behavioral Risk Factor Surveillance System (BRFSS) data. Facebook pages of 34 SHDs were studied over a 200 day period, coding 2597 posts into 19 broad health communication categories. Mean number of Facebook posts per SHD was 76.4 (range 34-133); most frequent topic areas included healthy living (12%), communicable diseases (9%), vaccines and immunization (7%), emergency preparedness and response (7%), infant and child health (5%), smoking and tobacco use (5%), and miscellaneous (32%). Through web-based interactive graphics (Google motion charts), we contrasted Facebook posts with CDC's BRFSS data on adult nutrition and physical activity, vaccination, smoking, adolescent health and road traffic accidents. Our research finds an apparent disconnect between content provided on Facebook by SHDs and the health conditions that affect their populations. Acknowledging the severe limitations in funding and human resources faced by the SHDs, our research attempts to present the factual situation in embracing a vastly popular social media platform for health communication. We believe there is a need for research exploring methods to balance the demands and resources.