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

Objective: 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 inter net 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. Method: 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. Results: 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. Conclusions: 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. Published by Elsevier Ltd.