Longitudinal study of influenza A virus circulation in a nursery swine barn

Table 5 Univariable associations for recurrent IAV shedding using logistic regression and Cox’s regression for recurrent events

Variable	Ordinary logistic regression			PWP-CP
Variable	OR	95% CI	p-value	HR	95% CI	p-value
Study 1^a
H3N2_A^c,d	0.63	0.37, 0.09	0.10	0.87	0.77, 0.99	0.03
H3N2_A²	1.63	1.13, 2.37	0.01	1.11	1.04, 1.17	0.01
H3N2_B^c,e	0.49	0.21, 1.10	0.08	0.83	0.68, 1.01	0.72
H3N2_B²	1.24	1.00, 1.53	0.04	1.04	0.99, 1.09	0.05
H1N1_C^c,f	–	–	–	0.87	0.78, 0.96	0.01
H1N1_home^c,g	1.19	0.53, 0.97	0.03	0.82	0.84, 0.98	0.01
“Low heterologous” H3N2 cluster	Baseline	–	–	Baseline	–	–
“High heterologous” H3N2 cluster^h	2.66	0.86, 8.24	0.08	1.15	0.91, 1.44	0.22
Source			<0.01^\\\			<0.01^\\\
Source 1	5.5	1.54, 19.6	0.01	2.58	2.14, 3.11	0.01
Source 2	0.68	0.15, 3.08	0.62	1.34	1.02, 1.76	0.03
Source 3	5.5	1.54, 19.6	0.01	2.16	1.77, 2.65	0.01
Source 4	Baseline	–	–	Baseline	–	–
Source 5	1	–	–	1.96	1.39, 2.76	0.01
Study 2^b
H3N2_B^c,e	0.36	0.10, 1.27	0.11	0.67	0.46, 0.98	0.04
H3N2_B²	1.15	0.96, 1.37	0.12	1.06	1.00, 1.12	0.03

OR: Odds Ratio, PWP-CP: Prentice, Williams and Peterson conditional probability.
^\\\ p-value obtained by testing categorical variable using a partial likelihood test.
^a,bTwo distinct longitudinal studies were performed in nursery pigs.
^cEstimates based on variable representing an hemagglutinin inhibition titer for a specific strain divided by 10 and then log2 transformed.
^dMaternally derived antibodies as measured by using H3N2 strain heterologous to the resident strain in Study 1 (93.8% similarity in the hemagglutinin).
^eMaternally derived antibodies as measured by using H3N2 strain heterologous to the resident strain in Study 1 (97.9% similarity in the hemagglutinin).
^fMaternally derived antibodies as measured by using H1N1 virus broadly classified as classical H1N1 virus.
^gMaternally derived antibodies as measured by using H1N1 strain detected in the Study 2 (i.e. homologous strain).
^hGroupings obtained from the cluster analysis based on hemagglutinin inhibition titers of strains heterologous to the resident virus in Study 1.

ISSN: 1297-9716