Objectives. To compare how human papillomavirus (HPV) vaccination was portrayed on Pinterest before and after the platform acted to moderate vaccine-related search results to understand (1) what the information environment looked like previously and (2) whether Pinterest's policy decisions improved this environment in terms of sources and content.Methods. In this quantitative content analysis, we compared 2 samples of 500 HPV vaccine-focused Pinterest posts ("pins") collected before and after Pinterest's actions to provide more reliable vaccine-related information. Pins were based on search results and were analyzed using the Health Belief Model.Results. The majority of preaction search results leaned toward vaccine skepticism, specifically focused on perceived vaccine barriers. Few pins were published by public health-related Pinterest accounts. Postaction search results showed a significant shift to HPV vaccination benefits, and the number of pins by government or medical accounts increased. However, the proportion of pins in search results containing HPV content of any type was significantly lower.Conclusions. Pinterest's efforts to moderate vaccination discussions were largely successful. However, the ban also appeared to limit HPV vaccination search results overall, which may contribute to confusion or an information vacuum.