Pneumococcal vaccine improves pulmonary clearance of live pneumococci after splenectomy

The efficacy of pneumococcal capsular polysaccharide vaccines after splenectomy to decrease the incidence of postsplenectomy pneumococcal sepsis is controversial. We examined the effect of pneumococcal vaccine on clearance of live pneumococci from lungs of splenectomized and sham-operated mice following an aerosol challenge of pneumococci. Splenectomy impaired clearance of pneumococci from mouse lungs and allowed for increased translocation of pneumococci to tracheobronchial lymph nodes compared to shams (P less than 0.01). Pneumococcal vaccine improved lung clearance in both splenectomized and sham-operated mice compared to saline controls (P less than 0.01), but the number of live pneumococci recovered from lung pairs was greater in splenectomized mice compared to shams (P less than 0.01). Pneumococcal vaccination facilitated earlier translocation of pneumococci to tracheobronchial lymph nodes, and probably promoted bactericidal activity in these nodes, in both splenectomized and sham-operated mice. Survival in splenectomized mice was improved by vaccination, but remained significantly less than that in saline-treated sham-operated mice (P less than 0.0009). The data show that pneumococcal vaccine can improve lung antipneumococcal defenses in splenectomized mice, but not to the same degree as in mice retaining their spleens. Pneumococcal vaccine should be given after splenectomy, but surgeons should caution patients that it may be less effective than when given to individuals with intact spleens or before elective surgery.