You risk the chance of the virus mutating or replicating/coming back at an aggressive form. However, that's if you miss a LOT. One or two days won't have any negative effect and you'll be fine. But don't do this often. Try to take it every day.
I don't know too much about the effects of missing dose.but my dr warned me not to missed frequently otherwise virus will be mutated means no effects of drug on virus in future