Father Finegan has drawn attention to a letter from the Vatican which says that it is not lawful to refuse Holy Communion on the tongue. The context of this is the way an English diocese has responded to the Swine Flu. The Vatican replied to someone who wrote to ask if, in this case, Communion on the tongue could be refused. The answer is a clear "No".
When I saw that some bishops were arguing that Communion in the hand was safer, or that the tongue was less safe, I wondered where they had got their information. A few years ago I did a basic hygiene course, and it was clear from that, that the most dangerous part of the body - as regards passing on contamination (short of spitting at people or coughing in their face!) is the hand.
A week or so ago I was in Chicago and a friend there who has been doing some research on these things told me about a survey done in the United States regarding infection etc. He said the researchers had discovered that the most dangerous objects with regard to passing on infection are supermarket trolleys. He told me that in some supermarkets antiseptic wipes are provided. He agreed with me that it is the hand - above all - that is the danger. I couldn't help noticing that when I give Communion on the tongue I can do it, quite easily, without touching the mouth or the tongue of the communicant. On the other hand (no pun intended), when I give Communion in the hand it is almost impossible not to touch someone's hand now and then.
Swine Flu aside, this is an issue (Reception of Holy Communion) that will not go away. I found this article which discusses the question of Communion on the hand. I thought it interesting. It was written before the Swine Flu scare but gives some insight into how the change in the distribution of Holy Communion came about.