What happens if the first dose of hepattis B was not given within the first 24 hours?

All infants should receive their first dose of hepatitis B vaccine as soon as possible after birth, preferably within 24 hours.
When not feasible, the birth dose can still be effective in preventing perinatal transmission if given within 7 days, particularly within 3 days, although somewhat less than if given within 24 hours, but with declining effectiveness with each passing day. Even after 7 days, a late birth dose can be effective in preventing horizontal transmission and therefore remains beneficial.
All infants receive the at birth dose during the first contact with health facilities at any time up to the time of the first primary dose.
Any at birth dose given after 24 hours should be reported as a late birth dose vaccination