How can I protect newborn puppies from parvo?

2 puppies from our female's (Roxy) last litter contracted parvo and died. We're not sure if Roxy had been vaccinated as a puppy or not, however she did not contract it herself. Two nights ago she gave birth to another litter & I'm worried about the possibility of her ping it to her puppies. The puppies are inside the house but Roxy goes back and forth. Some say to spray the yard with a bleach solution and others say bleach won't kill parvo but it will kill the gr and to use something called "Shacklee Basic G" If the puppies can't be vaccinated until 6 weeks old is there anything else I can do to help protect them?