The effectiveness of influenza vaccine among elderly Chinese: A regression discontinuity design based on Yinzhou regional health information platform

Figures & data

Figure 1. Influenza vaccination rate following age profile.

Table 1. The change of influenza vaccination rate at age 70 years.

	All	Male	Female
Change in rate at age 70 years	29.1 (28.2–29.9)	26.4 (24.9–27.9)	31.6 (30.7–32.5)
Rate under 70 years	4.8	4.6	4.9
Underlying Observations	195109	95707	99402

The numbers are influenza vaccination rates per 100 people. Estimates of change rate are followed by 95% confidence intervals. A person’s age is defined as the vaccination date subtract from the birth date. Rates are estimated based on the number of people alive during the study period. The regressions are estimated based on rates for one-year age cells for the population aged 60 to 80 inclusive. The regressions include a second-order polynomial in age fully interacted with an indicator for being 70 or over. The regressions are weighted by the number in each age group.

Figure 2. Change in hospital admission rate following age profile.

Table 2. Effectiveness of influenza vaccination on hospital admission.

Outcomes	Any cause	Pneumonia or influenza	Respiratory	Circulatory	Respiratory or circulatory
All
Change in admission rate at age 70 y	−8.8 (−20.2, 4.7)	−2.0 (−8.2, 4.1)	−3.4 (−18.2, 11.5)	−17.3 (−50.7, 16.0)	−18.1 (−47.6, 13.5)
Admission rate below age 70 y	368.4	6.8	33.7	145.3	158.3
Effectiveness (95% CI), %	8.2 (−36.8, 51.3)	8.3 (−40.4, 69.2)	23.8 (−16.9, 67.5)	30.2(−27.8, 83.4)	31.5 (−25.7, 78.3)
Men
Change in admission rate at age 70 y	−34.2 (−77.6, 12.9)	1.9 (−10.3, 18.2)	−11.5 (−38.1, 15.0)	−22.4 (−76.9, 30.2)	−24.9 (−69.3, 29.4)
Admission rate below age 70 y	417.7	8.4	41.0	162.0	180.5
Effectiveness (95% CI), %	29.4 (−34.9, 75.7)	−23.5 (−75.4, 45.5)	40.1 (−18.6, 88.8)	41.1 (−24.6, 89.3)	43.2 (−23.1, 88.3)
Women
Change in admission rate at age 70 y	16.7 (−22.6, 56.0)	−5.2 (−24.3, 34.1)	3.9 (−7.8, 25.6)	−9.7 (−45.8, 26.5)	−8.1(−40.8, 22.7)
Admission rate below age 70 y	305.2	6.1	25.1	122.5	130.1
Effectiveness (95% CI), %	−27.7 (−61.9, 33.1)	38.0 (−22.1, 82.7)	−19.4 (−65.9, 33.0)	21.6 (−39.3, 79.7)	19.6 (−35.2, 76.8)

The numbers are admission rate per 10000 and vaccine effectiveness. All regressions include month-of-birth dummies. The regressions also include a quadratic polynomial in age fully interacted with an indicator variable for age ≥70 y. The regressions are weighted by the average number of people in age-month. Hospital admissions are included in a category if there is any mention of the condition on the discharge diagnosis. The ICD 10 codes included in each category are as follows: influenza and pneumonia, J09–J18; respiratory diseases, J00–J99; and circulatory diseases, I00 –I99. The hospital admissions are included between September 2020 and March 2021. CI: confidence interval.

Figure 3. Change in mortality rate following age profile.

Table 3. Effectiveness of influenza vaccination on mortality.

Outcomes	Any cause	Respiratory or circulatory
All
Change in admission rate at age 70 y	−2.7 (−16.4, 9.9)	−1.6 (−10.9, 7.8)
Mortality rate below age 70 y	14.5	3.0
Effectiveness (95% CI), %	13.1 (−34.2, 61.8)	20.1 (−43.7, 87.3)
Men
Change in admission rate at age 70 y	−3.1 (−10.7, 4.6)	−5.3 (−28.1, 16.9)
Mortality rate below age 70 y	28.8	9.3
Effectiveness (95% CI), %	28.6 (−23.6, 79.5)	35.7 (−20.1, 89.5)
Women
Change in admission rate at age 70 y	9.9 (−22.1, 40.8)	16.9 (−30.2, 62.4)
Mortality rate below age 70 y	10.1	2.1
Effectiveness (95% CI), %	−25.5 (−76.4, 30.7)	−21.7 (−87.3, 44.5)

The numbers are mortality rate per 10000 and vaccine effectiveness. All regressions include month-of-birth dummies. The regressions also included a quadratic polynomial in age fully interacted with an indicator variable for age ≥70 y. The regressions are weighted by the average number of people in age-month. Deaths are included in the category of primary cause from medical certificates of the dead. The ICD10 codes included in each category are as follows: respiratory diseases, J00–J99; and circulatory diseases, I00 –I99. The dead is included between September 2020 and March 2021. CI: confidence interval.

Data availability statement

The data can be shared upon request to the corresponding authors in a collaborative research approach.