Table 2 Serotype‐specific antibody responses to polysaccharide antigens.

Pneumococcus	Response of patient 1 (age 5¾ years) μg/ml	Response of patient 2 (age 2½ years) μg/ml	Normal responses (age >3 years ) μg/ml
Serotype 3	3.02	1.4	>0.74
Serotype 4	0.22	0.1	>0.91
Serotype 6B	0.34	0.17	>0.68
Serotype 9N	0.54	0.46	>0.97
Serotype 14	0.55	0.3	ND
Serotype 18C	0.75	0.18	>0.58
Serotype 19F	0.9	0.26	>1.79
Serotype 23F	ND	<0.4	ND

For patient 1, data show specific antibody concentrations 2 weeks after immunisation with Pneumovax 23 plus the conjugate pneumococcal vaccine Prevenar (and 3 months after the secondary invasive pneumococcal disease caused by serotype 14). For patient 2, data show specific antibody concentrations 2 weeks after immunisation with Pneumovax 23 and 3 months after the last of a series of four monthly immunisations with Prevenar (13 and 7 months after the two episodes of invasive disease caused by Streptococcus pneumoniae serotypes 23F and 33F). Of the serotypes shown, 4, 6B, 9V, 14, 18C, 19F and 23F are present in both vaccines. Concentrations of specific antibodies were determined by ELISA (μg/ml). As a reference, the US Pneumococcal Reference Serum Lot 89‐SF was used. Normal responses were determined in 37 children (aged 4–15 years; distribution: 1, 8, 12 and 16 for the age groups 3–4, 5–6, 7–9, and 10–15 years, respectively). Antibody levels were determined 2–3 weeks after vaccination with Pneumovax. Cut‐off values given are the 5th percentile for the total group of controls. ND, not done.