I'd be inclined not to have him vaccinated.
Do you think your insurance is good value at his age? I ask this because when Charley reached ten years of age M&S raised his insurance premium to £589. I also had to pay the first £70 of any claim, plus 20% of the remainder. I refused to renew my insurance and accepted that I would take a hit if needed. Two years later Charley had a malignant melanoma removed from his back paw, and the total cost was about £490. Thus, I had saved two years premiums, and I guess the premium would have increased again when he became eleven.
Unless you are paying a low premium with a low excess, it may not pay you to continue with his insurance, and by not having him vaccinated there will be nothing to lose. However, it is very unlikely that he will suffer anything due to no vaccination at his age. He will have developed sufficient immunity, and particularly as he does not mix with other dogs.