Among recipients of 7-valent pneumococcal conjugate vaccine , increased serotype-specific serum IgG was associated with a reduction in nasopharyngeal acquisition of serotype 23F ( relative risk , 0.53 ; 95 % confidence interval , 0.31-0 .93 ) but was not associated with a reduction in acquisition of serotype 19F ( relative risk , 1.07 ; 95 % confidence interval , 0.57-2 .03 ) .
