TABLE 1.

Compliance with sampling and numbers of paired sera sent for serology by age group

Age group (mo)	No. of children
	Planned	Agreed to participate	First visit	Second visit	Paired sera sent for serology
6	100	70	61	44	44
12	100	76	63	46	46
18	100	80	67	49	49
24	100	92	79	68	68
36	100	95	81	78	78
48	100	100	98	93	93