Table 1.

Characteristics of US travellers with one reported dose of yellow fever vaccine and yellow fever virus plaque reduction neutralization test (PRNT) results by time since last vaccination

	Vaccination <10 years prior to serum collection N = 155 No. (%)	Vaccination ≥10 years prior to serum collection N = 66 No. (%)	P-valuea
Femaleb	80 (52)	35 (53)	0.88
Median agec (range)	37 (2–78)	57 (14–77)	<0.01d
Immunosuppressione	8(5)	14 (21)	<0.01
YF titer ≥1:10f	146 (94)	54 (82)	0.01

^aFisher exact unless otherwise noted.

^bSex missing for five individuals.

^cAge missing for 26 individuals.

^dWilcoxon rank sum.

^eTravellers were considered immunosuppressed if infected with HIV, had received an organ transplant within 10 years, or was specifically noted to be immunosuppressed on the test request form.

^fTiters ≥1:10 are considered positive using PRNT with a 90% cutoff.