The user asked why someone would claim that the side effects of the Covid-19 vaccines are mild and not to be feared. The response provided information based on a scientific publication that looked at serious adverse effects of the vaccine and found that they were similar to those of traditional vaccines, such as pain at the injection site, muscle aches, and fever in some cases. It also mentioned that allergic reactions were very rare and not fatal. Overall, the information presented suggests that the side effects of the Covid-19 vaccines are generally mild and not a cause for significant concern.