Table 1.

Association of mortality with influenza circulating in population: vaccinated and unvaccinated people

	No (rate*) of deaths
Cause of death	In high influenza period	Outside high influenza period	Association of mortality (95% CI) with influenza index†	Modification of “influenza” effect by vaccination‡	Deaths (%) attributable to influenza§
All causes
Unvaccinated	564 (13.9)	2305 (9.4)	1.16 (1.04 to 1.29)	1	13.4
Vaccinated	346 (9.7)	1630 (7.7)	1.02 (0.90 to 1.16)	0.89 (0.80 to 0.98)	2.2
Cardiovascular
Unvaccinated	226 (5.6)	1050 (4.3)	1.19 (1.05 to 1.36)	1	16.3
Vaccinated	145 (4.1)	772 (3.7)	1.03 (0.85 to 1.26)	0.87 (0.73 to 1.02)	3.2
Respiratory
Unvaccinated	156 (3.9)	380 (1.6)	1.31 (0.92 to 1.87)	1	23.9
Vaccinated	97 (2.7)	293 (1.4)	1.05 (0.75 to 1.47)	0.80 (0.69 to 0.93)	5.1
Other
Unvaccinated	182 (4.5)	875 (3.6)	1.00 (0.86 to 1.16)	1	0
Vaccinated	104 (2.9)	565 (2.7)	0.98 (0.80 to 1.21)	0.98 (0.82 to 1.17)	0

^*Crude annual mortality (%).

^†Exponentiated regression coefficient scaled to represent mortality at 90th centile relative to zero influenza period. Adjusted for month (indicators for 40 strata), temperature (linear term for two week mean of degrees below 20), and number of days since 31 December separately in vaccinated and unvaccinated people.

^‡Ratio (95% confidence interval) of exponentiated coefficients in previous column, estimating impact of vaccination on tendency for mortality to increase during periods of high counts of circulating influenza.

^§Fraction of deaths attributable to influenza at 90th centile of circulating influenza.