From what i understand, strep bacteria are everywhere, like MRSA, and staph are too. and the Prevnar vax is no guarantee against not coming down with invasive strep infection, and studies indicate the vax may be responsible for mutation of the bacteria. Does your son go to school, play at playgrounds and go out in the general public without complications? If so, then you should be okay, esp if your son goes to daycare or school--kids get vaxed for that all the time and harbor those bacteria with no outward infection at all......how did they know if was strep pneumo in his ears? did they do a culture?
has your child had a problem with strep throat in his 5yrs?
I cannot tell you more about the illness itself - I know that there are other moms on this board who are way more knowledgeable about this than I. However, what I do want to do is to support you and tell you that you should go with your gut and tell this person not to visit. At the end of the day, you and your child's health is the most important - not what others think of you. Obviously, the thought of possibly contracting this is stressing you out - that in and of itself is your body's way of telling you NO. These folks are moms too and they should understand that you are making the best choice that you can for your family.
Best of luck to you. Hope you all are well.