At the time when COVID-19 knocks our doors and we need to stay inside not to let it come in, it becomes especially important to take measures to boost your immune system as isolation puts it at severe risk. You can find lots of articles on it on the Internet. Here are a few to start with:
https://www.today.com/health/easy-ways-boost-your-health-while-under-quarantine-t178713
https://thriveglobal.com/stories/8-expert-tips-to-boost-your-immune-system-while-in-self-quarantine/