Table 1. Summary statistics for individuals’ ages at the time of serum collection and the timing of collections for specimens in the DoD Serum Repository.

	Mean	Standard Deviation	Median
Age at date of collection, years a	27.7	8.9	25
Specimens per person	3.9	3.9	2
Years between specimens b	1.1	0.8	1
Years between first and last specimens	6.4	5.6	4

a. The maximum legal age for service members is between 17 and 62 years with few exceptions, so only those who were 17–70 years of age were included. Outliers were dropped.

b. A total of 4,642,870 individuals provided only 1 specimen.