Background The onset of the COVID-19 pandemic and the concurrent development of vaccines offered a rare and somewhat unprecedented opportunity to study antivaccination behavior as it formed over time via the use of archived versions of websites. Objective This study aims to assess how existing antivaccination websites modified their content to address COVID-19 vaccines and pandemic restrictions. Methods Using a preexisting collection of 25 antivaccination websites curated by the IvyPlus Web Collection Program prior to the pandemic and crawled every 6 months via Archive-It, we conducted a content analysis to see how these websites acknowledged or ignored COVID-19 vaccines and pandemic restrictions. Websites were assessed for financial behaviors such as having storefronts, mention of COVID-19 vaccines in general or by manufacturer name, references to personal freedom such as masking, safety concerns like side effects, and skepticism of science. Results The majority of websites addressed COVID-19 vaccines in a negative fashion, with more websites making appeals to personal freedom or expressing skepticism of science than questioning safety. This can potentially be attributed to the lack of available safety data about the vaccines at the time of data collection. Many of the antivaccination websites we evaluated actively sought donations and had a membership option, evidencing these websites have financial motivations and actively build a community around these issues. The content analysis also offered the opportunity to test the viability of archived websites for use in scholarly research. The archived versions of the websites had significant shortcomings, particularly in search functionality, and required supplementation with the live websites. For web archiving to be a viable source of stand-alone content for research, the technology needs to make significant improvements in its capture abilities. Conclusions In summary, we found antivaccination websites existing prior to the COVID-19 pandemic largely adapted their messaging to address COVID-19 vaccines with very few sites ignoring the pandemic altogether. This study also demonstrated the timely and significant need for more robust web archiving capabilities as web-based environments become more ephemeral and unstable.

BACKGROUND The onset of the COVID-19 pandemic and concurrent development of vaccines offered the rare opportunity to study anti-vaccination behavior as it formed. OBJECTIVE Assess how anti-vaccination website content addressed COVID-19 vaccines METHODS Using a collection of 25 anti-vaccination websites curated by the IvyPlus Web Collection Program prior to the pandemic and crawled every 6 months via Archive-IT, we conducted a content analysis to see how these websites acknowledged or ignored COVID-19 vaccines. Websites were assessed for financial behaviors, mention of COVID vaccines, references to personal freedom, safety concerns, and skepticism of science. RESULTS The majority of websites addressed COVID-19 vaccines in a negative fashion, with more websites making appeals to personal freedom or expressing skepticism of science than questioning safety. Many of the anti-vaccination websites we evaluated actively sought donations and members. The content analysis also offered the opportunity to test the viability of archived websites for use in scholarly research. The archived versions of the websites had significant shortcomings and required supplementation with the live websites. CONCLUSIONS In summary, we found anti-vaccination websites existing prior to the COVID-19 pandemic largely adapted their messaging to address COVID-19 vaccines. Our study also demonstrated the timely and significant need for more robust web archiving capabilities.