Background: Invasive pneumococcal disease (IPD) is an infectious disease where Streptococcus pneumoniae can be detected in the cerebrospinal fluid or blood.Methods: Eight patients presented to our hospital with adult IPD. We compared with 69 cases of pneumococcal pneumonia treated in our department between 2012 and 2014. None of the patients had a history of pneumococcal vaccine administration.Results: Hematological examination showed the platelet count was significantly lower and the serum C-reactive protein level was significantly higher in the IPD group. There was a significant difference in the use of a respirator and mortality in the IPD group. About antibiotics, Carbapenem and quinolone were used for the treatment of many patients in the IPD group. In the fatal three cases of IPD, the age of all members were 65 years or younger. Two of three had no underlying disease.Conclusion: IPD develops without elderly people and in those without underlying disease. Also, the patients who took a sudden course may result in death. In line with previous studies that have reported the effectiveness of the pneumococcal vaccine, our study findings emphasize the need of administering vaccination for prevention of IPD in person who was younger than 65 years old.