With the worldwide data showing that invasive Hib disease has been practically eliminated in many countries, and considering the demonstrated security of the vaccine, it should be promptly adopted to the national immunization program in Korea. a monovalent and another on a combination PRP-OMP vaccine. Thus, a meta-analysis was conducted only around the tetanus toxoid conjugate vaccine (PRP-T). After a primary series of 2 doses and 3 doses, 80.6% (95% confidence interval [CI]; 76.0-85.1%) and 95.7% (95% CI; 94.0-98.0%) of infants achieved an antibody level 1.0 g/mL, respectively. The immunogenic response to the PRP-T vaccine was acceptable after a primary series of 3 doses and also 2 doses. A reduced quantity of doses as a main series could be cautiously considered in Korean infants. Keywords:Haemophilus influenzaetype b, Vaccines, Immunity, Meta-analysis == INTRODUCTION == Haemophilus influenzaetype b (Hib) was an important cause of bacterial meningitis and other serious invasive diseases among children aged <5 yr before the introduction of the Hib conjugate vaccines (1). A dramatic decrease in Hib disease burden was noted in countries that launched the Hib conjugate vaccine into program immunization schedules (2). Four basic different types of conjugate vaccines have been licensed for use in infants against Hib diseases. These vaccines differ in the carrier proteins, structure Cenicriviroc and length of the capsular polysaccharide molecule, polyribosylribitol phosphate (PRP) and the method of conjugating the carrier protein to the polysaccharide. The first conjugate produced was the diphtheria toxoid conjugate (PRP-D), followed by mutant diphtheria toxin conjugate (PRP-CRM), meningococcal outer membrane protein conjugate (PRP-OMP) and tetanus toxoid conjugate (PRP-T). Hib conjugate vaccines have been shown to be highly efficacious against invasive Hib disease and safe in clinical trials (3-5). Vaccine efficacy of Hib vaccines are assessed in correlation with the level of production of specific anti-PRP IgG (6). An anti-PRP level 1.0 g/mL is considered predictive for long-term protection from invasive disease in a vaccinated populace (7). Based on this, the WHO recommendations on evaluating the efficacy of Hib conjugate vaccines have been released, e.g. effective vaccines induce 1.0 g/mL of anti-PRP antibody in 70% or more of infants 1 month Cenicriviroc after completion of the primary immunization series (8). With the known security and proven effectiveness of the Hib conjugate vaccines, WHO recommends it to be included in all routine infant immunization programs, regardless lack of local surveillance data (9). By the end of the year 2005, Hib vaccines were included in the program infant immunization program in 101 out of 192 WHO member countries (10). However, it is not yet introduced into the national immunization program in Korea. To make important decisions around the policy for Hib vaccination, a nationwide study around the epidemiologic status in relation to the disease burden of invasive Hib diseases as well as cost-effectiveness study is urgent. Also, the appropriate routine should be decided. The Hib vaccination routine differs between countries in quantity of doses and periods of vaccination. At present, the current recommendations for the vaccination routine for Hib vaccine in Korea is usually that the primary series be given at 2, 4 and 6 months of age for the PRP-T and PRP-CRM vaccine and at 2 and 4 months of age for the PRP-OMP vaccine, with a following booster dose at 12-15 months of age for all those three types of vaccines. Although all countries give a booster dose of the Hib vaccine, some countries recommend 2 doses as a main series, whereas other countries Cenicriviroc recommend 3 doses before 12 months of age. The objective of this study was to evaluate the immunogenicity of a main series of Hib conjugate vaccines in Korean infants through a meta-analysis. We will therefore determine whether the immunologic responses are acceptable after 3 doses (given at 2, 4, and 6 months of age) and also after 2 doses (given at 2 and 4 months of age) of the Hib conjugate vaccine. == MATERIALS AND METHODS == == Literature search == MEDLINE, KoreaMed, and the Korean Medical Database were searched for all studies of Hib conjugate vaccine in Korean children. The search included terms in the title or key words, applying the terms ‘Haemophilus influenzaetype b’, ‘Hib’, ‘vaccination OR vaccine’ and ‘immunogenicity’. Also, a manual search of studies was carried out on studies referenced in publications identified through the initial search and experts on Hib vaccine in Korea were contacted for unpublished data or ongoing studies. == Selection criteria == We included RGS9 all clinical trials that reported immunogenicity results following a main series (immunization at 2, 4, and 6.