Vaccines are powerful weapons that save humanity from many infectious diseases. However, vaccine hesitancy is still deeply rooted in Japan, and more than 2,800 women a year die of cervical cancer, for example. Just as all drugs have side effects, there are no vaccines with no adverse events. Not every event that occurs after a vaccination is necessarily a adverse reaction. We must be fully aware of this and make appropriate judgments, taking into consideration the risks of infections.