They haven't kept that data until
VAERS was implemented in 1990.
But doing a quick-ish search of the VAERS database for 2024 alone shows there were 59 registered deaths in children under the age of 18 associated with adverse vaccine reactions.
Doing a random screening of years I found 211 child deaths to associate with vaccines in 1995, 120 in 2000, 135 in 2007, 155 in 2009 and 48 in 2019
If we average those out we get 121 annually as a rough estimate. If we project that out over 50 years we get ~6,000 deaths of children connected to adverse vaccine reactions in 50 years.