Quinvaxem is 5 in 1 vaccine which comprises: diphtheria, pertussis, tetanus, HBV and act-Hib. The vaccine has been officially introduced into Vietnam EPI since June 2011. In this descriptive study, the authors monitor and assess the advert events of Quinvaxem injected to children less than 1 year of age in EPI in Ha Long city, Quang Ninh in 2011. Advert even is defined and classified under WHO guild1ine. The result shown that no severe case as anaphylactic shock, death or hospitalize after immunization. There were some mild cases but still in normal rate. The mild and on spot of injection cases reported include: painful 59.5 percent
inflamation 49.2 percent
fever 84.3 percent (86.5 percent is mild fever). The advert evens were not clutstered. Mostly within 6 hours after injection. 100 percent cases recover with no effect. Inconclusion, Quinvaxem vaccine has been safely implemented for children under 1 year of age in Ha Long city, Quang Ninh, 2011. The continuing of advert event mornitoring especially for new vaccine is very important to deliver immunization safety to community.