I'm a 18 years old Brazilian student, almost finishing High School. I have a lot of interest in biology and I want my career to have the highest impact possible. So, I believe that working on this issue would be the best choice for me.
However, I'm unsure about what graduation would be the best for me to pursue; should I study Biological Sciences, or is there a more suitable course?
We at Condor Camp (a project for longtermist movement building in Brazil) are providing some advice for Brazilian students, feel free to reach out: info@condor.camp. I studied Law in a Brazilian university, so I have some first-hand knowledge about the Brazilian higher ed system but not about Biology exactly. My guess is that Biology degrees in Brazil can often be quite narrow, and that there might be more interesting alternatives depending on where you're located and how competitive your ENEM grades were. I recommend you reach out for a chat with one of our team members :)
My two cents (not knowing anything about biology/pandemics):
If you want to do almost anything related to science of any kind, I would recommend getting a solid grounding in math, statistics, and computer programming in addition to your content-specific studies (e.g. biology or epidemiology). This will give you vastly greater options to adjust your career as you go than if you just do some specific content area (e.g. biology). It will also likely also help you understand the particular content area much better.
Toward this end, I would consider doing a double major like 1) math, statistics, or computer science and 2) your content area [e.g. biology]. If you can only do one major, I would choose the technical major (e.g. applied math) rather than the content major (e.g. bio).
I don't have any domain expertise, but you may want to have a look at the 80,000 Hours website, in particular the biorisk career profile (see "How to enter the field"), though if you're new to EA it may make sense to begin with the introductory material.