Table 2.

Vaccine effectiveness estimated against influenza-associated hospitalization against all influenza and against influenza A(H3N2), by age, and in a sensitivity analysis removing children positive for SARS-CoV-2.

	Total	Influenza positive			Influenza negative			Vaccine effectiveness*
		nvac	N	Proportion vaccinated (%)	nvac	N	Proportion vaccinated (%)	%	95% CI
Any influenza
All ages (9m-17y)	3183	194	528	36.7	992	2655	37.4	22.3	−11.9 to 46.0
9 months to 3 years	1401	17	146	11.6	242	1255	19.3	32.7	−28.7 to 64.9
4 to 8 years	1346	115	244	47.1	598	1102	54.3	13.2	−46.1 to 48.4
9 to 17 years	436	62	138	44.9	152	298	51.0	8.8	−129.8 to 63.8
All influenza, removing SARS-CoV-2 positives
All ages (9m-17y)	3074	193	526	36.7	963	2548	37.8	24.4	−9.0 to 47.6
9 months to 3 years	1333	17	145	11.7	233	1188	19.6	34.9	−24.3 to 65.9
4 to 8 years	1328	115	244	47.1	584	1084	53.9	10.3	−51.3 to 46.8
9 to 17 years	413	61	137	44.5	146	276	52.9	26.3	−91.4 to 71.6
Influenza A(H3N2)
All ages (9m-17y)	3074	164	419	39.1	992	2655	37.4	14.3	−29.3 to 43.1
9 months to 3 years	1362	14	107	13.1	242	1255	19.3	27	−53.0 to 65.2
4 to 8 years	1295	98	193	50.8	598	1102	54.3	−2.8	−86.7 to 43.4
9 to 17 years	417	52	119	43.7	152	298	51.0	11.3	−148.4 to 68.4
Influenza A(H3N2), removing SARS -CoV-2 positives
All ages (9m-17y)	2965	163	417	39.1	963	2548	37.8	16.7	−26.0 to 44.9
9 months to 3 years	1294	14	106	13.2	233	1188	19.6	29.2	−47.8 to 66.1
4 to 8 years	1277	98	193	50.8	584	1084	53.9	−6.7	−94.4 to 41.5
9 to 17 years	394	51	118	43.2	146	276	52.9	31.5	−99.0 to 76.4

^*Estimated as (1 minus the adjusted conditional odds ratio)x100%, with adjustment for age, sex, underlying medical conditions, prior vaccination and conditioning on calendar time.