Factors influencing survival of BALB/c mice and their effects on immune efficacy in an experiment of hepatitis B immunization

There was an accidental death of BALB/c mice in the course of the experiment about hepatitis B immunization. The reasons of the mice breeding failure were analyzed in order to provide some experience for future animal preparation about hepatitis B immunization. Items of all mice including sex, age, dose of hepatitis B vaccine (HepBVac), dose of hepatitis B immunoglobulin (HBIG), immunization route, vaccination schedule and the acclimatization period were recorded before the first immunization. Among 334 mice included, the survival rates in different groups of initial ages were 45.9% in 3-week-old, 49.3% in 4-week-old, 51.9% in 5-week-old, 84.8% in 7-week-old and 96.6% in 8-week-old; the survival rate in seven days acclimatization group was 96.6% and 53.3% in one day acclimatization group. Multivariate logistic regression analysis indicated that smaller ages (3 weeks, 4 weeks) and acclimatization for only one day were the independent risk factors affecting the survival of mice. Multivariate logistic regression analysis showed that injection with HBIG, lower dose of HepBVac and hypodermic injection were independent risk factors for low-and non-response to HepB Vac. It is suggested that the mice should be more than five-week-old and must have acclimated to the environment for one week before the experiment begins. The initial ages of the mice have no impact on their immune efficacy. Key words: BALB/c mice, age, acclimatization, hepatitis B immunization.