Estimating bias from internet non-use for a hybrid web vaccination survey - 2013-2017 Behavioral Risk Factor...

To maintain acceptable response rates, the cost has grown for vaccination surveys that use traditional data collection modes, such as face-to-face and telephone interviews. Conducting a web or internet survey could be a low-cost alternative. However, because the internet is not used by everyone, we need to study how prevalence estimates in web surveys for vaccination surveillance could be affected by internet non-use.

We analyzed data from the 2013-2017 Behavioral Risk Factor Surveillance System to assess undercoverage biases from internet non-use by partitioning into proportion of internet non-users and difference in prevalence of influenza and pneumococcal vaccinations between internet and internet non-users, respectively.

The proportion of internet non-users decreased monotonically from 43.3% in 2013 to 35.4% in 2017; however, the undercoverage bias from internet use for pneumococcal vaccination increased from 0.8 to 1.5 percentage points at the same time. Overall, the undercoverage bias was -1.1 and 1.5 percentage points for influenza vaccination and pneumococcal vaccination in 2017, respectively. For both vaccinations, we found large absolute and relative biases among certain demographic subgroups.

Although the proportion of internet non-users decreased in recent years, undercoverage bias of hybrid internet survey for influenza and pneumococcal vaccinations did not decrease. Despite a small overall undercoverage bias, the bias in subpopulation groups was not negligible.