TABLE 4.

Anti-MSP1₁₉ 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)
Total Ig	95.7	97.0	1.000	0.667 (0.134, 1.775)	0.418 (0.118, 1.084)	0.636
IgG1	66.0	72.7	0.627	0.362 (0.037, 1.206)	0.315 (0.061, 0.673)	0.973
IgG2	6.4	9.1	0.687	0.014 (0.006, 0.024)	0.012 (0.007, 0.029)	0.476
IgG3	40.4	45.5	0.819	0.017 (0.004, 0.082)	0.014 (0.008, 0.114)	0.338
IgG4	0.0	0.0	—b	−0.001 (−0.005, 0.008)	0.000 (−0.003, 0.004)	0.696
IgM	34.0	42.4	0.488	0.312 (0.252, 0.536)	0.389 (0.233, 0.580)	0.513

^aSee Table 2, footnotes a, b, and c. The threshold for significance is 0.0085 after an adjustment is made for the number of comparisons. 

^b—, not compared due to negative value in both groups.