Table 2.

IgG antibody reactivity with crude malaria antigen and EB200 in Senegalese individuals grouped by age and data on their experience of clinical attacks of malaria

	IgG reactivity in ELISA (mean ± s.d.)*
Age group (n) (years)	Crude antigen	EB200‡	Individuals with clinical attack†	Number of attacks over 1 year	Mean number of attack per person
4–9 (17)	0·47 ± 0·21	0·10 ± 0·16	52·9%	23	1·35 (0–5)
10–14 (17)	0·51 ± 0·19 (P = 0·45)	0·24 ± 0·35 (P = 0·22)	29·4%	15	0·88 (0–8)
15–19 (14)	0·73 ± 0·27 (P = 0·013)	0·91 ± 0·75 (P = 0·001)	7·1%	1	0·07 (0–1)
20–87 (49)	0·92 ± 0·33 (P = 0·054)	1·11 ± 0·67 (P = 0·27)	6·1%	3	0·06 (0–1)
Total (97)	0·74 ± 0·28	0·73 ± 0·54	18·5%	42	0·43
Controls (9)	0·15 ± 0·03	0·01 ± 0·01

^*Sera were assessed for antibody reactivity at dilutions of 1 : 1000. Logarithmic absorbance values were used for unpaired Student's t-test. The P-values refer to the statistical difference between the indicated group and the age group above.

^†Percentage of individuals in the group that suffered from one or more clinical attacks of malaria as defined by febrile illness (temperature = 38·5°C) coinciding with parasitaemia level over an age-dependent threshold level previously defined in this village [23]. The 97 individuals shown in the table were actively monitored for a period of 1 year starting immediately after the blood sampling for antibody analysis was taken. They were present in the village during 94 ± 15% of the year of follow-up.

^‡Reactivity with EB200 was estimated by subtracting the reactivity with GST from the reactivity with GST-EB200.