TABLE 1.

Antibody concentrations in sera of toddlers vaccinated with meningococcal C conjugate vaccine or meningococcal polysaccharide vaccine, as assessed by different assays^a

Assay, method, and vaccine	Geometric mean			Probabilityb
	Preimmu- nization	Post- dose 1	Post- dose 2	Post- dose 1	Post- dose 2
IgG anticapsular antibody
Standard ELISAc
Polysaccharide vaccine	0.12	7.0	9.7
				0.11	0.81
Conjugate vaccine	0.18	5.1	9.3
Modified ELISAd
Polysaccharide vaccine	0.22	1.0	1.2
				<0.001	<0.001
Conjugate vaccine	0.20	4.8	21.0
Bactericidal antibodye
Polysaccharide vaccine	4.2	14	16
				<0.001	<0.001
Conjugate vaccine	4.4	74	761

^aSerum samples were selected from toddlers showing a wide range of IgG antibody responses to vaccination. There were 35 subjects in the polysaccharide group and 35 in the conjugate group (see Materials and Methods). 

^bComparing respective geometric mean antibody concentrations or titers elicited by the two vaccines. 

^cIn micrograms per milliliter. 

^dIn units per milliliter. 

^eReciprocal of titer.