He was found unconscious by hikers in Sai Kung and was sent by the Government Flying Service to Eastern Hospital where he was pronounced dead.
The Department of Health said he appeared to be fine while getting the jab at an inoculation centre in San Po Kong last Thursday.
Authorities will investigate the cause of death.
He is the eleventh person in Hong Kong to die after a Covid vaccination. Nine of the cases involved Sinovac and two involved BioNTech.
A panel of experts said the previous deaths were probably caused by pre-existing health conditions, instead of the jabs.
Several countries, including France, have suspended flights to and from Brazil due to fears over the more contagious coronavirus variant spreading there.