<prompt> In a 3 year old most common cause of Hepatitis B isPin prickSaliva exchangePerinatalBlood transfusion  <response>: HBV is transmitted through contact with blood and body fluids of an infected person . In highly endemic areas , HBV infections occur mainly due to perinatal transmission resulting from carrier mothers to their infants during first 5 years of life. It may also occur through horizontal transmission from casual contact . HBV is not transmitted by breastfeeding Reference : OP Ghai pgno 217 9th edition. 