Heterogeneity of the efficacy of the 23-valent pneumococcal polysaccharide vaccine caused by various underlying conditions of chronic pulmonary disease in older patients: prospecti... by Satoshi Morita, Satoshi Inoue, Takashi Sato, Yoshiaki Ishigatsubo, Shunsaku Mizushima, Yuji Watanuki, Tetsuji Kaneko, Naoki Miyazawa, Takeshi Kaneko, Yutaka Natsumeda