['Nasal vaccination is an effective therapeutic regimen for preventing otitis media. Since cholera toxin (CT) is toxic, an alternative adjuvant is required for the development of a nasal vaccine. The efficacy of CpG oligodeoxynucleotide (ODN) as a mucosal adjuvant was examined.', 'Mice were immunized intranasally with P6 protein of non-typeable Haemophilus influenzae (NTHi) and adjuvant, CT, or CpG ODN, and P6-specific antibody responses were examined. The expression of P6-specific cytokine mRNA in splenic CD4 T cells was also determined. In addition, NTHi challenges were performed and the NTHi was quantified in nasal washes.', 'P6-specific IgA in nasal wash and serum IgG titers were elevated significantly after nasal immunization. The IgG1/IgG2a ratio in serum from P6+CpG-immunized mice was less than that of P6+CT-immunized mice. Although IL-6 was expression similarly in both groups, IFN-gamma expression was greater in P6+CpG-immunized mice than in P6+CT-immunized mice. Enhanced clearance of NTHi from the nasopharynx was also shown equally in both groups.'] Does nasal vaccination with CpG oligodeoxynucleotide induce protective immunity against non-typeable Haemophilus influenzae in the nasopharynx?