Table 2.

HAI Responders versus Alternate responders versus No response

	PCR-positive HAI respondersa (n=117)	PCR-positive HAI non-respondersa with alternate responseb (n=18)	PCR-positive No response (n=14)	P-value
Male	52 (44%)	6 (33%)	8 (57%)	0.4037
Age				0.4248
0–14 years	79 (68%)	12 (67%)	7 (50%)
15+ years	38 (32%)	6 (33%)	7 (50%)
Symptoms
Feverc	99 (85%)	13 (72%)	9 (64%)	0.1070
ILId	95 (81%)	13 (72%)	7 (50%)	0.0274
ARIe	108 (92%)	15 (83%)	8 (57%)	0.0006
Illness duration (mean days, SD)
Cough	7.39 (3.54)	6.14 (4.00)	5.41 (4.49)	0.0933
Shedding	4.23 (3.07)	3.72 (2.87)	2.71 (1.90)	0.1732
Pre-exposure antibody levels (mean level, SD)
HAI	11.41 (16.28)	5.27 (1.18)	19.23 (28.64)	0.0757
HA full	41.59 (71.69)	38.45 (101.14)	104.78 (99.81)	0.0173
HA stalk	36.57 (54.96)	27.21 (47.57)	116.75 (138.87)	0.0001
NA	13.11 (19.44)	9.90 (8.34)	23.93 (31.88)	0.1131

Data are no. individuals with characteristic/no. of individuals.

Abbreviations: ILI, influenza-like illness; ARI, acute respiratory infection; SD, standard deviation; HAI, hemagglutinin inhibition assay; HA, hemagglutinin; NA, neuraminidase.

^aHAI non-responder is an individual who failed to generate a 4-fold or greater HAI response; HAI responder is an individual who generated a 4-fold or greater HAI response.

^bAlternate response is a 4-fold or greater response to HA full, HA stalk, or NA.

^cFever is reported fever or measured temperature ≥ 37.5 °C.

^dILI is fever as described above plus either cough or sore throat.

^eARI is defined as any of the following symptoms: fever, cough, sore throat, runny nose.