Apologies - I'm typing in my phone and hit the wrong key.
It's worth remembering, and forgive me if you already know this, that any one of the three vaccinations will provide immunity, provided it is given at the point when maternal antibodies are no longer present.
Maternal antibodies interfere with the seo-conversion of the vaccination. Between weaning and the point, at around 14 weeks, when maternal antibodies are probably no longer present, puppies are very vulnerable to infection.
Giving 3 vaccinations is an attempt to provide protection at the earliest possible moment. The problem is that unless you do titre testing, you won't know which of the set of injections has been effective.
So your puppy might be protected 2 weeks after the first vaccination or not until 2 weeks after the 3rd vaccination. That's why keeping them out of public places until 16 weeks is safer. You don't have to give up in socialisation - but be conscious of them mixing with vaccinated dogs in areas which are clean.
Parvo, particularly is omnipresent, so even visitors to your home might carry it in. The good news is that because of the presence of parvo, most dogs will have some residual resistance.