When I first started taking the antiviral medication Zovirax I had no health insurance and so I could only buy a few pills at a time and the pharmacist told me that if I didn't take at least a weeks worth of the medication that I'd be putting my immune system at risk. And what really annoys me is that with all the Dr's. I've asked about this not one had any knowledge of antivirals causing my immune system to be compromised. Let's not forget the pharmacist that said exactly that. So what is it yes they can? Or without a shadow of a doubt they cannot cause an immune disorder?