Blood type is a bit more complicated then that, there are a total of 36 different blood group systems each containing or not containing certain antigens. So even amongst type O blood there are still rarer types of type O blood. People with type O- blood are just more likely to not have certain antigens which viruses bind to in a person's blood. So first question of you being type O would be are you O+ or O-? Then if you're O- which of the possible 61 antigens found on the Rh blood group system do you not have. You can request this info if/when you are getting blood work done.

I for instance would be O Rhnull, I don't have any of the 61 antigens found on the Rh blood group which makes my blood even more rare even amongst the O- group already. Bad side is I can't accept O- blood from others who do have Rh antigens because my immune system would reject it. Bright side my system is more resistant to viruses in general. Not immune I just generally get hit less hard then others and am less likely to get viral infections under the same circumstances as others.