Table 1.

Attributes and definitions for adult respondents ^a

Attribute	Definition
Seriousness of illness	This is how bad or serious the illness would be for you if you got sick.
Duration of illness	This is how long you would have symptoms of the illness if you got sick.
Vaccine effectiveness	This is the likelihood that you will NOT get the illness that the vaccine can prevent if you are vaccinated. Vaccines with greater effectiveness are better at reducing your risk of illness and death.
Your risk of illness without vaccination	This is the likelihood you will get the illness that the vaccine can prevent if you are not vaccinated.
Your risk of death without vaccination	This is the likelihood you will die from the illness that the vaccine can prevent if you are not vaccinated.
Your risk of severe side effect from vaccination	This is the likelihood that after vaccination, you will get a serious long-term or permanent disability that affects your nervous system. You would no longer be able to do daily activities because of the side effect. The side effect is caused by what is in the vaccine.
Length of time vaccine has been available	This is the number of years that the vaccine has been available to the public in the United States.
Location	This is the place you go to get vaccinated.
Time	This is the total time it would take you to get one shot of the vaccine, including: (1) Time you wait (2) Time you spend with the health care professional (3) Travel time to and from the location where you get the vaccine.
Type of health care professional giving vaccine	This is the type of healthcare professional who gives you the vaccine.
Primary care provider recommendation	This is the recommendation of your primary care provider about getting the vaccine. A primary care provider is the person you see for regular medical care and can be a doctor, a nurse practitioner (NP) or a physician assistant (PA).
Cost after insurance	This is the amount that your family would pay for you to receive the vaccine. This amount would not be covered by insurance. You would be paying with money that you have available today.

^aAttributes were the same for adolescents and parents, but definitions differed slightly. Additional attributes included risk of illness with vaccination and risk of death with vaccination which were derived by multiplying the risk of illness/death without vaccination by the vaccine effectiveness. These additional attributes and their levels are available in Additional file 2: Table S2