Vaccinations and viruses are in everyone’s mind at the moment.
A good resource to learn more about them, and the complicated workings of our immune system, is a series of videos on this course on edX:
The videos are a few years old, so the Coronavirus is not specifically mentioned, but the overall topic is very relevant. The videos try to be catchy and accessible even if you haven’t studied a lot of biology. If you need more background, you can start with the first introductory units.
EdX is a platform for online learning with courses from many universities and institutions from all over the world. You can watch most courses for free, and pay only if you want to get a certificate or get access to exams etc. Highly recommended!