Introduction. Haemophilus influenzae type b (Hib) is responsible for many severe diseases, including epiglottitis, pneumonia, sepsis, and meningitis, particularly in young children. The Hib conjugate vaccine is considered protective and safe. The evidence of protection afforded by Hib vaccines in the context of real-world immunization programs is essential for accelerating and sustaining their uptake worldwide. The objective of the study was to evaluate the effectiveness of Hib conjugate vaccine among children aged 2 to 59 months in the Republic of Moldova. Material and methods. We designed and carried out a matched case–control study in two main pediatric hospitals in Chisinau, Republic of Moldova: Institute of Mother and Child and the Municipal Children’s Clinical Hospital no. 1, between December 2020 – January 2022. The endpoint for this case-control vaccine effectiveness study was non-specific, clinically confirmed pneumonia, thus the cases were children with established diagnosis of pneumonia, according to World Health Organization criteria. The cases were matched by age and sex with up to three controls who do not have pneumonia and came for treatment at the health center where the research was carried out during the same period as the case group. Results. To evaluate the effectiveness of Hib vaccine, there were enrolled 89 patients and 267 children in the control group. Vaccine effectiveness (VE) was calculated as (1 – Mantel-Haenszel OR in vaccinated children compared to unvaccinated children) x100%. Thus, the VE of Hib vaccine was revealed to be about 63%, (OR=0.37; CI 95%: 0.15 – 0.89; p < 0.05). Conclusions. Hib vaccination is significantly associated with the prevention of pneumonia in children under five years in the Republic of Moldova. It is mandatory to ensure policies that encourage and support the extension of immunization programs targeting high-risk groups. Future efforts to further reduce the disease burden of Hib infections remain a high priority.