The rationale for this study is to assess the change in ambulatory care visit rates for acute otitis media between the period before (2001-2009) and after the introduction of the 13-valent pneumococcal conjugate vaccine (13vPnC) (2011-2013) among children less than 5 years old in the United States.

NAMCS-The survey utilizes a three stage sampling design based on (1) probability of selecting a primary sampling unit (PSU) (2) probability of selecting a physician within the PSU and (3) probability of selecting a patient within the physician practice. This last probability is defined to be the exact number of office visits during physician's specified reporting week divided by the number of patient record forms completed. NHAMCS- For producing unbiased national estimate, this survey utilizes four stages (a) Probability of selecting a PSU (b) probability of selecting a hospital with in PSU (c) probability of selecting an emergency department (ED) or outpatient department (OPD) within the hospital (d) probability of selecting a visit within ED or OPD. The overall probability of selection is the product of the probabilities at each stage. The inverse of the overall selection probability is the basic inflation weight.

Inclusion Criteria:

Five years of age or under at the time of visit, ambulatory visit for otitis media, myringotomy tube insertion, skin rash or trauma during study period

Exclusion Criteria:

Age over 5 years, no ambulatory visits for the events listed in inclusion criteria

National Ambulalatory Medical Care Survey (NAMCS)-national sample of visits to non federally employed office based physicians who are primarily engaged in direct patient care, and National Hospital Ambulatory Medical Care Survey (NHAMCS)- national sample of visits to emergency and outpatient departments and to ambulatory surgery facilities in noninstitutional general and short stay hospitals, exclusive of Federal, military, and Veterans Administration hospitals, located in the 50 States and the District of Columbia