TABLE 3.

Ig-specific anti-MSP4 antibodies in Vietnam residents susceptible to and potentially protected against P. falciparum infection based on the presence or absence of P. falciparum parasitemia during the surveillance period^a

Isotype	Antibody prevalence (%)			Median antibody level (OD)
	Susceptible (n = 47)	Protected (n = 33)	P (χ2)	Susceptible (n = 47)	Protected (n = 33)	P (U)
IgG1	87.2	66.7	0.027	0.132 (0.071, 0.555)	0.204 (0.031, 0.674)	0.584
IgG2	27.7	36.4	0.408	0.010 (0.005, 0.031)	0.010 (0.004, 0.053)	0.914
IgG3	76.6	72.7	0.694	0.360 (0.060, 1.082)	0.241 (0.048, 0.726)	0.476
IgG4	0	3.0	0.230	0.002 (−0.001, 0.005)	0.002 (0.000, 0.003)	0.445
IgM	23.4	21.2	0.817	0.164 (0.109, 0.283)	0.132 (0.089, 0.232)	0.485

^aSee Table 2, footnotes a, b, and c. The threshold for significance is 0.0102 after an adjustment is made for the number of comparisons.