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A rebuttal to “A new discussion for Effects of annual influenza vaccination on mortality and hospitalization in elderly patients with ischemic heart disease: A nationwide population-based study”
Preventive Medicine 57 (2013) 69
Contents lists available at SciVerse ScienceDirect
Preventive Medicine journal homepage: www.elsevier.com/locate/ypmed
Letter to the Editor A rebuttal to “A new discussion for Effects of annual influenza vaccination on mortality and hospitalization in elderly patients with ischemic heart disease: A nationwide population-based study” Keywords: Censored data Death incidence rate Number needed to vaccinate
We thank Dr. Moghadam for his comments (Moghadam, 2013) on our recent report on the effects of influenza vaccination in Taiwan (Liu et al., 2012). In this study, we used a sampling cohort dataset released by the Taiwan National Health Research Institute. This dataset contained every patient's demographics, diagnosis and treatments in outpatient and hospital claims so we had complete follow-up data. All patients in this dataset were censored for death and termination of insurance because of death. We separated our patients into vaccinated and non-vaccinated groups based on the vaccination status in 2002. In our report (Liu et al., 2012), Table 1 showed that some comorbidities were different between two groups. Using the Cox proportional-hazards model, we first performed the univariable analysis to identify variables associated with outcomes. Variables with P value less than 0.05 were included in the multivariable analysis. Although some variables were significantly different between two groups in 2002, these variables failed to predict endpoints in the univariable analysis and subsequently were not included in the multivariable analysis. In our study, the overall death incidence rate was 94.3 deaths per 1000 person-year [95% confidence interval (CI): 89.8–99.0] (180.9 deaths per 100,000 person-week, 95% CI: 172.2–189.9). The mean death incidence rate was 170.2 per 100,000 person-week (95% CI: 158.3–182.7) in the influenza season and 191.7 (95% CI: 179.0– 204.9) in the non-influenza season.
In the influenza season, the death incidence rate of vaccinated patients was 93.5 per 100,000 person-week (95% CI, 80.7–107.8) and 233.2 (95% CI, 214.5–253.1) in non-vaccinated patients. The mean number needed to vaccinate to save a death was 29 (95% CI: 25–35). In the non-influenza season, the death incidence rate of nonvaccinated patients was 155.3 (95% CI, 138.5–173.4) per 100,000 person-week and 221.6 (95% CI, 203.3–241.0) in non-vaccinated patients. The mean number needed to vaccinate was 55 (95% CI: 41–86). We provide a Table 1 which showed the number of death, death incidence rate, risk difference and number needed to vaccinate to save a death in the influenza and non-influenza seasons of each year. Conflict of interest statement The authors declare that there are no conflicts of interests.
References Liu, I.F., Huang, C.C., Chan, W.L., et al., 2012. Effects of annual influenza vaccination on mortality and hospitalization in elderly patients with ischemic heart disease: a nationwide population-based study. Prev. Med. 54, 431–433. Moghadam, M.D., 2013. A new discussion for “effects of annual influenza vaccination on mortality and hospitalization in elderly patients with ischemic heart disease: a nationwide population-based study”. Prev. Med. 56, 163.
I-Fan Liu Department of Medicine, Taipei Veterans General Hospital, Taoyuan Branch, Taoyuan, Taiwan Hsin-Bang Leu Healthcare and Management Center, Taipei Veterans General Hospital, Taipei, Taiwan Corresponding author. Fax: + 886 2 28757735. E-mail address: [email protected].
Table 1 Death in influenza and non-influenza season between 2002 and 2006 in Taiwan. 2002–2003 Influenza season Mortality Vaccinated 74 Non-vaccinated 167 Death incidence rate per 100, 000 person-week Vaccinated (95% CIa) 104.6 (82.1–131.2) Non-vaccinated (95% CI) 292.7 (250.0–340.6) Risk difference (%) (95% CI) 4.6 (3.4–5.8) b NNV (95% CI) to save a death 22 (18–30) a b
2003–2004
2004–2005
2005–2006
Non-influenza season
Influenza season
Non-influenza season
Influenza season
Non-influenza season
Influenza season
Non-influenza season
109 109
21 164
40 179
50 122
97 142
44 120
67 113
153.6 (126.1–185.3) 193.1 (158.6–233.0) 1.1 (−0.1–2.3) 93 (44–∞)
92.4 (57.2–141.3) 172.8 (147.4–201.4) 2.1 (0.9–3.39) 47 (30–111.1)
180.8 (129.2–246.3) 188.2 (161.6–217.9) 0.2 (−1.4–1.84) 442 (55–∞)
87.1 (64.7–114.9) 248.3 (206.2–296.5) 4 (2.8–5.2) 25 (20–37)
169.2 (137.2–206.4) 290.7 (244.8–342.6) 3.3 (1.8–4.8) 31 (21–56)
85.9 (62.4–115.3) 268.8 (222.9–321.4) 4.5 (3.2–5.8) 23 (18–32)
130.8 (101.4–166.1) 253.2 (208.7–304.4) 3.3 (1.9–4.8) 30 (21–53)
CI = confidence interval. NNV = number needed to vaccinate.
0091-7435/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ypmed.2013.02.025
Contents lists available at SciVerse ScienceDirect
Preventive Medicine journal homepage: www.elsevier.com/locate/ypmed
Letter to the Editor A rebuttal to “A new discussion for Effects of annual influenza vaccination on mortality and hospitalization in elderly patients with ischemic heart disease: A nationwide population-based study” Keywords: Censored data Death incidence rate Number needed to vaccinate
We thank Dr. Moghadam for his comments (Moghadam, 2013) on our recent report on the effects of influenza vaccination in Taiwan (Liu et al., 2012). In this study, we used a sampling cohort dataset released by the Taiwan National Health Research Institute. This dataset contained every patient's demographics, diagnosis and treatments in outpatient and hospital claims so we had complete follow-up data. All patients in this dataset were censored for death and termination of insurance because of death. We separated our patients into vaccinated and non-vaccinated groups based on the vaccination status in 2002. In our report (Liu et al., 2012), Table 1 showed that some comorbidities were different between two groups. Using the Cox proportional-hazards model, we first performed the univariable analysis to identify variables associated with outcomes. Variables with P value less than 0.05 were included in the multivariable analysis. Although some variables were significantly different between two groups in 2002, these variables failed to predict endpoints in the univariable analysis and subsequently were not included in the multivariable analysis. In our study, the overall death incidence rate was 94.3 deaths per 1000 person-year [95% confidence interval (CI): 89.8–99.0] (180.9 deaths per 100,000 person-week, 95% CI: 172.2–189.9). The mean death incidence rate was 170.2 per 100,000 person-week (95% CI: 158.3–182.7) in the influenza season and 191.7 (95% CI: 179.0– 204.9) in the non-influenza season.
In the influenza season, the death incidence rate of vaccinated patients was 93.5 per 100,000 person-week (95% CI, 80.7–107.8) and 233.2 (95% CI, 214.5–253.1) in non-vaccinated patients. The mean number needed to vaccinate to save a death was 29 (95% CI: 25–35). In the non-influenza season, the death incidence rate of nonvaccinated patients was 155.3 (95% CI, 138.5–173.4) per 100,000 person-week and 221.6 (95% CI, 203.3–241.0) in non-vaccinated patients. The mean number needed to vaccinate was 55 (95% CI: 41–86). We provide a Table 1 which showed the number of death, death incidence rate, risk difference and number needed to vaccinate to save a death in the influenza and non-influenza seasons of each year. Conflict of interest statement The authors declare that there are no conflicts of interests.
References Liu, I.F., Huang, C.C., Chan, W.L., et al., 2012. Effects of annual influenza vaccination on mortality and hospitalization in elderly patients with ischemic heart disease: a nationwide population-based study. Prev. Med. 54, 431–433. Moghadam, M.D., 2013. A new discussion for “effects of annual influenza vaccination on mortality and hospitalization in elderly patients with ischemic heart disease: a nationwide population-based study”. Prev. Med. 56, 163.
I-Fan Liu Department of Medicine, Taipei Veterans General Hospital, Taoyuan Branch, Taoyuan, Taiwan Hsin-Bang Leu Healthcare and Management Center, Taipei Veterans General Hospital, Taipei, Taiwan Corresponding author. Fax: + 886 2 28757735. E-mail address: [email protected].
Table 1 Death in influenza and non-influenza season between 2002 and 2006 in Taiwan. 2002–2003 Influenza season Mortality Vaccinated 74 Non-vaccinated 167 Death incidence rate per 100, 000 person-week Vaccinated (95% CIa) 104.6 (82.1–131.2) Non-vaccinated (95% CI) 292.7 (250.0–340.6) Risk difference (%) (95% CI) 4.6 (3.4–5.8) b NNV (95% CI) to save a death 22 (18–30) a b
2003–2004
2004–2005
2005–2006
Non-influenza season
Influenza season
Non-influenza season
Influenza season
Non-influenza season
Influenza season
Non-influenza season
109 109
21 164
40 179
50 122
97 142
44 120
67 113
153.6 (126.1–185.3) 193.1 (158.6–233.0) 1.1 (−0.1–2.3) 93 (44–∞)
92.4 (57.2–141.3) 172.8 (147.4–201.4) 2.1 (0.9–3.39) 47 (30–111.1)
180.8 (129.2–246.3) 188.2 (161.6–217.9) 0.2 (−1.4–1.84) 442 (55–∞)
87.1 (64.7–114.9) 248.3 (206.2–296.5) 4 (2.8–5.2) 25 (20–37)
169.2 (137.2–206.4) 290.7 (244.8–342.6) 3.3 (1.8–4.8) 31 (21–56)
85.9 (62.4–115.3) 268.8 (222.9–321.4) 4.5 (3.2–5.8) 23 (18–32)
130.8 (101.4–166.1) 253.2 (208.7–304.4) 3.3 (1.9–4.8) 30 (21–53)
CI = confidence interval. NNV = number needed to vaccinate.
0091-7435/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ypmed.2013.02.025