If you don't have Parma ham use another cured ham (Serrano, San Daniele, Jambon de Bayonne) or just an ordinary smoked ham, smoked bacon or even pancetta. I like the dried cured meats in this as they add a great flavour and a slightly different texture than normal ham.
You can make this without the ham and you could add a pinch of chilli flakes to the onion and herb mix to make it a bit spicy.
If you want to taste more of the vodka, don't add it to the sauce but add it to he pan with the pasta and butter in. This gives you a more intense flavour. If you add it to the sauce and boil off the vodka then you are only left with about 5% of the original alcohol which is not a lot but seems to unlock the flavour of the tomatoes - I love either way.