 The communication of science to the public needs to be stellar if people are going to be convinced to follow public health guidelines and recommendations. But science communicators face a problem. They need to better understand how people respond to scientific information that they see online. And they need to understand how people respond when scientific recommendations change. Understanding how the public responds to changes in science can help science communicators create relevant, timely, clearer and stronger messages that could improve the uptake of the latest and best available public health recommendations. During the COVID-19 pandemic, public health guidelines have changed as scientists have had time and opportunities to study the virus. How people respond to these changes tells us something about their likelihood to adhere to public health guidelines. Our research team wanted to know how do people react to changes in scientific information? There are different ways to answer this question. We approached it by studying social media data. We compared and contrasted two public discussions taking place on Twitter between April and June of 2020. One that focused on face masks and one that focused on COVID-19 vaccines. We chose this time frame because at the time public health recommendations about masks were changing, but recommendations about vaccines were not. By comparing tweets on both masks and vaccines, we could better understand how the public was responding to public health guidelines. We examined nearly 700,000 tweets that mentioned the word mask or vaccine in a data set specific to COVID-19. We found that mask-related tweets over this time period were more emotionally charged than tweets about vaccines. They contained more language that suggests pleading or distrust, such as words like please and hoax. We also found that mask-related tweets were less focused on scientific research than vaccine-related tweets. They included fewer words like science or research. While we might assume that the topic of masks would be less emotionally charged than that of vaccines, our data shows that, in fact, changes to public health recommendations seem to provoke strong emotional responses. Our findings suggest that science and health communicators can anticipate strong emotional responses to changes in public health recommendations. Such information may circulate rapidly online. It is important for communicators to anticipate emotional responses related to changing science. Public communication about changing science could be developed with this in mind. For instance, if public health communicators need to recommend changes to public health guidelines, they should dedicate equal time to crafting clear and succinct explanations for changes to be circulated alongside the new instructions. The reasoning for changes should be clear and explicit. Thanks for watching. You can find more details about this study in the video description. And if you like this video, please share it with your friends.