ABSTRACT
The effect of Streptococcus pneumoniae polysaccharide vaccine on homozygous sicklers was studied. The bactericidal and opsonizing functions of the serum were measured by five indices: i. The viability index of S. Pneumoniae type 2 in 10% serum. ii. viability following ingestion by human neutrophils iii. overall viability in presence of serum and neutrophils iv. effect of neutrophils on extra-cellular bacterial survival and v. Phagocytic index. Five sickle sera defective in all of the five indices before vaccination were restored to normal function after the patients had received 14-valent pneumovaccine. The comparison of the prevaccination and postvaccination sera was done with pooled white serum as control. The effect of the antibody alone in the postvaccination serum remained low inspite of the normal restoration. The maximum effect on any of the five indices was exerted when both the antibody and the heat labile factors are present together in the serum