Primary study on a freeze-dried Haemophilus influenzae type b conjugate vaccine

Objective To prepare a freeze-dried Haemophilus influenzae type b (Hib) polysaccharide conjugate vaccine and evaluate its safety and stability.Methods The vaccine was freezedried by using 2.5％ lactose as stabilizer.The safety was evaluated in terms of pyrogen,abnormal toxicity,toxicity reverse of tetanus toxoid,and allergenicity.The stability of vaccine was determined by an accelerated stability test at 37 ℃ for 28 days.Immunogenicity was detected by a routine ELISA.Results The safety analysis showed that the vaccine met requirements.The increase of body temperature was ＜0.6 ℃ in 3 rabbits after immunization.All guinea pigs and mice survived the 7-day observation period and gained weight after test.All indicators were qualified after storing the vaccine at 37 ℃ for 28 days.The contents of polysaccharide and high molecular weight conjugate were 12-15 μg/dose and 82％-86％,respectively.Seroconversion rate was above 95％ in the immunized mice.Conclusions The freeze-dried Hib conjugate vaccine is safe and stable.The study lays the base for evaluating protective effect and determining validity period of the vaccine. Key words: Haemophilus influenzae, type b;  Vaccines, conjugate;  Freeze-dried;  Lactose; Immunogenicity