some truly awful attitudes displayed on this thread.
If OP's son declines to do the voluntary test, the researchers will have allowed for a certain proportion of test refusers and will be able either to compensate for that or to enrol others on the study.
He is ten FFS. He's old enough to decide. I think a responsible parent would talk him through what's involved and explain why it's important and exciting to be part of this study, but at the end of the day, this isn't like a vaccination. It's not directly benefiting him (eg, the parent should make the decision even if their child doesn't want to), it's a voluntary role in a study.
Some of the comments here, trying to imply that the OP has somehow terrified her child about this swab ... FFS. A ten year old is very capable of watching the news and absorbing what's going on by himself, but not necessarily of being able to process it as an older child or an adult would. He'll have seen people being swabbed on the news and might have thought 'Nope. Don't want to do that' for whatever reason he has.
Saying 'I can't imagine why you wouldn't want to compel him to have this done' frankly speaks more for the lack of imagination of those making that sort of comment. 
My own older son has some autistic traits (he has a younger and very autistic brother, and we see a fair amount of similarities) and I absolutely guarantee he wouldn't want to do the swab test. I've said absolutely nothing to him about it when we've seen it on the news. But he's very squeamish and sensitive about 'procedures' (you should hear the fuss he makes about having fingernails cut). He's 12. He's very smart and understands why these sorts of things are important but god, I hope I don't ever need to persuade him to do it.