Prevention of elderly pneumonia by BCG vaccination

迟发型超敏反应是辅助性T细胞1介导的获得性免疫的重要标志。由于患有结核菌素反应抑制的残疾老年人患肺炎的风险增加，我们研究了卡介苗(BCG)对这些受试者肺炎发生的影响。88例结核菌素反应低下的老年残疾患者随机分为卡介苗接种组(n=44)和不接种组(n=44)。在接受卡介苗接种的44例患者中，41例(93%)结核转阴率为93%(CT组)。67例年龄匹配的结核菌素反应阳性患者(PT组)也纳入其中。我们前瞻性地比较了这三组患者两年内肺炎的发展速度。在随访期间，NT组44名患者中有19名(42%)、CT组41名患者中有6名(15%)和PT组67名患者中有9名(13%)被诊断为新肺炎。根据COX回归模型，NT组与CT组发生肺炎的危险比为3.22(95%CI为1.03~9.96，P=0.03)。NT组肺炎住院率明显高于CT组，相对危险度为7.14(95%CI为1.41~36.1，P=0.03)。反之，CT组和PT组的肺炎风险无显著差异(P=0.70)。这些发现表明，接种卡介苗可以重新激活免疫系统，降低残疾老年人患肺炎的风险。

Delayed type hypersensitivity response to tuberculin is an important marker of T helper 1 mediated acquired immunity. Since the disabled elderly with depressed tuberculin responses show an increased risk of pneumonia, we examined the effect of Bacillus Calmette-Guerin (BCG) administration on the development of pneumonia in these subjects. Eighty-eight disabled older patients with depressed tuberculin responses were randomly assigned with BCG inoculation (n = 44) or without inoculation (n = 44, NT group). Forty-one (93%) of the 44 patients assigned with BCG inoculation showed positive tuberculin conversion (CT group). Sixty-seven age-matched patients with positive tuberculin responses (PT group) were also enrolled. We prospectively compared the rates of development of pneumonia for two years among these three groups. During follow-up, new pneumonia was diagnosed in 19 of the 44 patients (42%) in the NT group, 6 (15%) of the 41 patients in the CT group, and 9 (13%) of the 67 patients in the PT group. According to the Cox regression model, a hazard ratio of developing pneumonia in the NT group compared with the CT group was 3.22 (95% CI 1.03 -9.96, P = 0.03). Furthermore, the rate of hospitalization due to pneumonia was significantly higher in the NT group compared with the CT group with a relative risk of 7.14 (95% CI 1.41 -36.1, P = 0.03). Conversely, there was no significant difference in the risk of pneumonia between the CT group and the PT group (P= 0.70). These findings suggest that BCG inoculation could re-activate the immune system and reduce the risk of pneumonia in the disabled elderly.