TABLE 1.

Comparison of clinical outcomes between (partially) semi-immune and nonimmune travelers with imported malaria based on studies stratified by immunity status

Reference	Country of study	Study designa	Population(s)	Outcome	Findingsb
Farnert et al. (110)	Sweden	Retrosp.	(i) Africans, lived in Sweden for <1 year (n = 57); (ii) Africans, lived in Sweden for 1–4 years (n = 52); (iii) Africans, lived in Sweden for 5–9 years (n = 67); (iv) Africans, lived in Sweden for 10–14 years (n = 50); (v) Africans, lived in Sweden for ≥15 years (n = 74); (vi) Swedes (n = 186)	Presence of WHO-defined criterion for severe malaria	Africans having lived in Sweden for 10–14 years and ≥15 years were similar to Swedes concerning severe malaria, defined according to WHO criteria (9.7% and 10.0% vs 9.5%); Africans having lived in Sweden <10 years had lower proportions of WHO-defined severe malaria (range of proportions, 4.2% to 8.8%)
				Presence of severe clinical signs	Africans having lived in Sweden for ≥15 years had a proportion of severe signs similar to those of Swedes (8.1% and 6.5%, respectively); Africans having lived in Sweden <15 years had lower proportions of severe signs (range of proportions, 3.2% to 3.9%)
				ICU admission	Proportion of Africans having lived in Sweden for ≥15 years and being admitted to ICU similar to that of Swedes (9.2% and 9.7%, respectively); Africans having lived in Sweden <15 years were admitted to ICU less often (range of proportions, 3.2% to 6%)
Pistone et al. (7)	France	Retrosp.	(i) Africans, lived in France for ≥15 years (n = 106); (ii) Europeans (n = 240)	Presence of WHO-defined criterion for severe malaria	Adjusted OR, 0.25 (95% CI, 0.074 to 0.846), indicating less frequent occurrence of severe malaria in Africans
Bouchaud et al. (83)	France	Prosp.	(i) Africans, lived in France for a median of 14 (4 min, 45 max) years (n = 252); (ii) Europeans (n = 99)	Presence of WHO-defined criterion for severe malaria	Crude OR, 4.3 (95% CI, 1.6 to 11.9), indicating more frequent occurrence of severe malaria in Europeans
				Percent parasitemia	Mean parasitemia was lower in Africans than in Europeans (0.8% vs 1.4%; P = 0.007)
				Fever clearance time	Mean fever clearance time was shorter in Africans than in Europeans (40.1 ± 24.6 vs. 54.6 ± 24 h; P < 0.0001)
				Parasite clearance time	Mean parasite clearance time was shorter in Africans than in Europeans (56.1 ± 31.2 vs 62.5 ± 30.5 h; P = 0.03)
Phillips et al. (85)	UK	Prosp.	(i) Africans with main residency in the UK for preceding 12 months (n = 309); (ii) Asians (n = 94); (iii) Europeans (n = 79)	Presence of WHO-defined criterion for severe malaria	Compared with Africans, the adjusted OR for severe malaria was 8.05 (95% CI, 2.93 to 22.1) and 8.2 (95% CI, 2.94 to 22.9) for Asians and Europeans, respectively
				Presence of unfavorable outcomes	Compared with Africans, the adjusted OR for an unfavorable outcome was 4.78 (95% CI, 2.47 to 9.23) and 3.88 (95% CI, 1.96 to 7.71) for Asians and Europeans, respectively
				Length of hospitalization	Compared with Africans, hospitalization was, on average, 40% (95% CI, 19% to 64%) and 34% (95% CI, 14% to 57%) longer for Asians and Europeans, respectively (P < 0.001)
Koopmans et al. (112)	Netherlands	Prosp.	(i) Nonimmune patients (n = 246); (ii) partially immune patients (n = 198); (iii) semi-immune patients (n = 9)	Acute kidney injury (AKI)	Proportion of nonimmune patients with AKI (74%) was higher than proportion of nonimmune patients without AKI (55%) (P = 0.007); concordantly, the proportion of partially immune (26%) and semi-immune patients (0%) with AKI was lower than the proportion of partially immune (45%) and semi-immune patients (2%) without AKI (P = 0.06 and P value not applicable, respectively)

^aRetrosp., retrospective; Prosp., prospective.

^bProportions were extracted geometrically from figures, as they were not presented in the main text.