One of the best things you can do is to support your immune system and strengthen it. The NHS advice includes trying to eat well, hydrate properly, take regular exercise and get enough rest and sleep. If you are worried that you are more vulnerable it is worth speaking to your GP and consider self isolating to shield you from the risk of catching the virus. Anyone who is immuno-suppressed is considered to be at more risk from COVID-19, however these are usually people treated with drugs which suppress the immune system. Antibiotics are not in this category.