Considering Varicella (ChickenPox) booster for 8yo

8yo son reeived the 1st vaccination ~6 months, no booster since.  Considering booster this year, but concerned with harmful side effects near and long term.
"CDC: Merck's VARIVAX vaccine has a high failure rate and mass vaccination of American children has driven the disease into atypical older age groups where it can be far more dangerous. "

I've read the 1st shot is 80% effective for 'life' and the booster may not be needed but suggested for benefit of general population.  There are potential immediate side effects of this shot and the above CDC remark suggests we may increase the likely hood of his contracting more severe Shingles later in life.  Suggestions that it's better to take a chance that he is among the 80% group rather than do him a disservice by putting his later years in increased jeopardy.  That even if he is among the 20% group, contracting ChickenPox now will very likely be mild and provide better future benefits -without associated vaccine risks.

Have there been more recent authoritative publications which may help provide guidance?