How to say it nicely

Just Me • Have a 4 year old daughter and a Newborn GLOW baby girl born 22/04/15..so in love 💕
So my next door neighbour who is also a good freind has a 2 year old daughter and is expecting another in May. The thing is she doesn't agree with vaccinating kids. 
I feel awful because she is lovely but I don't want my newborn who won't be fully vaccinated yet (she will get her injections when she is called for them by doctor like my eldest was). How can I tell her in a nice way that I don't want to risk it? 
My 4 year old I don't mind playing because she fully vaccinated but not wanting to risk it for newborn