Flu vaccination: adults 65+ (percent) (Source: BRFSS)
Maryland - Allegany

In 2011, two methodological refinements were made to the Behavioral Risk Factor Surveillance System (BRFSS). The first was to expand the sample to include data received from cell phone users. This change was made to reflect the population better. The second change was to modify the statistical method to weight BRFSS survey data. The new approach simultaneously adjusts survey respondent data to known proportions of demographics such as age, race and ethnicity, and gender. Prior to 2011, the weighting method was post stratification, while in 2011 it is raking. Raking is better able to account for more demographic characteristics and multiple sampling frames. Because of these changes, data collected in 2011 and later cannot be appropriately compared to previous data, although new results should better reflect the health status of the United States (see {link:60739}).

In order to create multi-year estimates, two changes were made to the new data. First, respondents who only have cell phones were removed. Second, weights were created specifically for this purpose using the post stratification method. Those two changes make the 2011 data similar to the pre-2011 data and allowed multi-year estimates to be created, even though these estimates will not be as representative of the U.S. population as the single-year estimates using 2011 data without these changes.

Efforts to create a new small area estimate methodology that will allow use all of the improvements instigated with the 2011 data are currently taking place. Once available, that methodology will be used for estimates provided here.

This Indicator uses Age-Adjustment Groups:  65-74, 75+

Description The Behavioral Risk Factor Surveillance System (BRFSS) is a state-based system of telephone health surveys that collects information on health risk behaviors, preventive health practices, and health care access primarily related to chronic disease and injury. The survey was established in 1984. Data are collected monthly in all 50 states, Puerto Rico, the U.S. Virgin islands, and Guam.

MethodologyData collection is conducted separately by each state. The design uses state-level, random digit dialed probability samples of the adult (aged 18 and older) population. All projects use a disproportionate stratified sample design except for Guam, Puerto Rico, and the U.S. Virgin Islands who use a simple random sample design. The questionnaire consists of three parts: (1) a core component of questions used by all states, which includes questions on demographics, and current health-related conditions and behaviors; (2) optional CDC modules on specific topics (e.g., cardiovascular disease, arthritis), that states may elect to use; and (3) state-added questions, developed by states for their own use. The state-added questions are not edited or evaluated by CDC. Interviews are generally conducted using computer-assisted telephone interviewing (CATI) systems. Data are weighted for noncoverage and nonresponse.