Safety and immunogenicity of an indigenously developed Haemophilus influenzae type b conjugate vaccine through various phases of clinical trials

In view of the need for a cost effective Haemophilus influenzae type b ( Hib) conjugate vaccine, a lyophilized vaccine as capsular polysaccharide ( PRP) conjugated to tetanus toxoid ( Sii HibPRO) was indigenously developed by Serum Institute of India Ltd., Pune (SIIL). From 2004-07, this new vaccine underwent a series of clinical studies before its licensure by National Regulatory Authority (NRA). This paper discusses the results obtained during the clinical development of this vaccine. On finding the vaccine to be safe in animal toxicity studies, a Phase I single dose study was carried out to assess the safety profile of Sii HibPRO in healthy adult male volunteers. Subsequently, in Phase III pre-licensure study, immunogenicity and safety of Sii HibPRO was assessed and compared with Hib tetanus conjugate vaccine ( Act-HIB) of Aventis, France. Immunogenicity was evaluated based upon serum anti-PRP IgG antibody concentrations by ELISA at prevaccination and one month each after the second and third dose. Safety was evaluated by recording details of adverse events after each dose of the vaccine. Postvaccination after the third dose, there was 100% seroprotection ( anti PRP IgG titre >= 0.15 mu g/ml) in both the groups. Long term protection (>= 1 mu g/ml) was achieved in 95.2% and 98.06% infants in Sii HibPRO and Act-HIB groups, respectively. At 15 months, prior to booster dose, 30 children in each group were evaluated and all were found to be seroprotected. Post booster, all of them responded with a strong boost response. Safety of Sii HibPRO was re-established in the post marketing surveillance in which 2,739 doses were administered to 1,029 infants, in 23 cities across India.