Hep B1 Vaccine was not given after birth and Baby is of 4 weeks old and the Pediatrician mentioned will give at 45 days, will there be any complication..?
Hepatitis B1 vaccine should be given at birth as it is a highly contagious disease. If dose is missed at birth, then it should be given as early as possible. When hepatitis B vaccination is delayed, infants remain vulnerable to infection when they are most susceptible. Further doses are also delayed and complete immunity is not developed till a certain age when fellow kids already achieve the immunity. 90% of kids who get infected with virus early in life remain seriously sick with Hepatitis B disease for life.
Your pediatrician has decided to give at 45 days. There must be some reason behind it. Earlier, Hepatitis b vaccine used to be delayed in preterm infants till they reached the chronological age of 30 days, Now, that practice is shunned as being illogical. The reason being, that baby may not live that longer without any vaccination. The more practical apptoach is to receive the vaccination as per weight . The infants who weigh less than 2000g are weak and can not generate immune response. So, doctors now wait for baby to gain the desired weight of 2 kg and not the chronological age.
Read further https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3956928/