Evaluation of seasonal influenza vaccination effectiveness based on antibody efficacy among the institutionalized elderly in Japan

Influenza vaccination efficacy was evaluated in 114 institutionalized elderly people in 2002/03. Strain A/H3N2 was isolated; 44 and 8 subjects had sudden-onset fever (≥37.8 °C) and kit-diagnosed influenza, respectively. Odds ratios adjusted for age, sex, comorbidity, and vaccine strain (OR_adj) were determined using multiple logistic regression. Seroprotected patients (haemagglutination-inhibition antibody titre ≥1:40) had lower incidence of fever (OR_adj, 0.35; 95% confidence interval [CI], 0.09–1.28) and kit-diagnosed influenza (OR_adj, 0.35; 95% CI, 0.03–4.64) than patients without seroprotection (antibody efficacy, ∼65%). Seroprotective levels of vaccination-induced antibodies probably prevent influenza among the institutionalized elderly, although statistical significance could not be confirmed owing to the sample size.     

北京市2008—2010年老年人流行性感冒疫苗接种情况及影响因素分析

流行性感冒(流感)已经多次引起世界范围大流行.2009年王小莉等[1]用蒙特卡罗模型对北京市甲型H1N1流感感染人数进行了估算,约有180万人感染.接种疫苗仍是预防流感最经济有效的措施[2].本研究对北京市老年人在2008-2010年流感流行前后流感疫苗接种的情况及影响2010年接种流感疫苗的因素进行了调查.     

Factors associated with continued adherence to influenza vaccination in the elderly

Objective

We aimed to analyze the factors influencing continued adherence to influenza vaccination in elderly persons vaccinated in the preceding season.

Methods

Using a population-based vaccination registry, we evaluated the proportion of persons vaccinated against influenza in Navarre, Spain, in the 2010-11 season among non-institutionalized persons aged 65 years or over who had been vaccinated in the 2009-10 season. Logistic regression was used to analyze the influence of sociodemographic, clinical and health care factors.

Results

Of the 64,245 persons vaccinated against influenza in the 2009-10 season, 87% were vaccinated in the 2010-11 season. Continued adherence to vaccination increased with the number of physician visits per year. It was lower in women, in the 65-69 and ≥ 95 year age-groups, in those hospitalized or diagnosed with any major chronic condition in the previous year, and in persons with hematological cancer or dementia. Health districts and physicians with higher coverage in the previous season continued to have higher adherence in the following season.

Conclusions

People vaccinated against influenza in one season tend to be vaccinated in the following one. Sociodemographic, clinical and health care factors have a moderate effect on the continuity of vaccination, with the most important factor being the treating physician.     

Factors associated with a successful expansion of influenza vaccination among pregnant women in Nicaragua

BackgroundPregnant women are at risk of severe influenza disease and are a priority group for influenza vaccination programs. Nicaragua expanded recommendations to include influenza vaccination to all pregnant women in the municipality of Managua in 2013.MethodsWe carried out a survey among 1,807 pregnant women who delivered at public hospitals in the municipality of Managua to evaluate the uptake of influenza vaccination and factors associated with vaccination.ResultsWe observed a high (71%) uptake of influenza vaccination among this population, with no differences observed by age, education or parity of the women. Having four antenatal visits and five or more visits were associated with receipt of influenza vaccination (AORs: 2.58; 95% CI: 1.15, 5.81, and 2.37; 95% CI: 1.12, 5.0, respectively). Also, receipt of influenza vaccination recommendation from a health care provider was positively associated with receipt of influenza vaccination (AOR: 14.22; 95% CI: 10.45, 19.33).ConclusionsThe successful expansion of influenza vaccination among pregnant women in the municipality of Managua may be due to ready access to free medical care and health care providers’ recommendation for vaccination at health care clinics that received influenza vaccine.     

Knowledge and attitudes towards influenza and influenza vaccination among pregnant women in Kenya

BackgroundInfluenza vaccination during pregnancy benefits mothers and children. Kenya and other low- and middle-income countries have no official influenza vaccination policies to date but are moving towards issuing such policies. Understanding determinants of influenza vaccine uptake during pregnancy in these settings is important to inform policy decisions and vaccination rollout.MethodsWe interviewed a convenience sample of women at antenatal care facilities in four counties (Nairobi, Mombasa, Marsabit, Siaya) in Kenya. We described knowledge and attitudes regarding influenza vaccination and assessed factors associated with willingness to receive influenza vaccine.ResultsWe enrolled 507 pregnant women, median age was 26 years (range 15–43). Almost half (n = 240) had primary or no education. Overall, 369 (72.8%) women had heard of influenza. Among those, 288 (78.1%) believed that a pregnant woman would be protected if vaccinated, 252 (68.3%) thought it was safe to receive a vaccine while pregnant, and 223 (60.4%) believed a baby would be protected if mother was vaccinated. If given opportunity, 309 (83.7%) pregnant women were willing to receive the vaccine. Factors associated with willingness to receive influenza vaccine were mothers’ belief in protective effect (OR 3.87; 95% CI 1.56, 9.59) and safety (OR 5.32; 95% CI 2.35, 12.01) of influenza vaccines during pregnancy.ConclusionApproximately one third of pregnant women interviewed had never heard of influenza. Willingness to receive influenza vaccine was high among women who had heard about influenza. If the Kenyan government recommends influenza vaccine for pregnant women, mitigation of safety concerns and education on the benefits of vaccination could be the most effective strategies to improve vaccine acceptance.     

流感疫苗对老年慢性阻塞性肺疾病患者干预效果观察

目的观察流感疫苗对老年慢性阻塞性肺疾病（COPD）患者病情干预效果。方法选取112例老年COPD稳定期患者,对照组54例给予常规解痉、平喘、化痰治疗,接种组58例在此基础上给予流感疫苗接种,观察两组患者1年内的病情发展情况及疫苗接种组的不良反应。结果接种组患者1年内急性发作次数（2.91±1.70）、急性期病程（38.78±17.63）d及因急性发作住院次数（1.03±0.61）次、住院天数（12.36±6.32）d,明显低于对照组[分别为（5.22±2.14）、（49.63±21.25）d、（1.98±0.84）次、（17.73±7.85）d],差异有统计学意义（P〈0.01）;肺功能指标及6分钟步行距离测试两组差异无统计学意义（P〉0.05）;接种组局部反应发生率5.17%,未见全身不良反应。结论老年COPD患者接种流感疫苗后不良反应率低且轻微,可降低急性发作次数及住院次数,但对肺功能、运动耐力的改善、病死率等尚需追踪观察。     

Effectiveness of the influenza vaccination program for the elderly in Taiwan

Background and objectives

Since 1998, an influenza vaccination program has been implemented by the Taiwan government targeting people aged ≥65 years. However, the evidence of the effectiveness of this program in preventing influenza, which is based on the nation-wide database, is lacking. This study attempted to estimate the effectiveness of the influenza vaccination program in preventing influenza- and pneumonia-associated outpatient visits and hospitalization in the elderly.

Methods

Randomly sampled data of 1 million claims from the National Health Insurance Research Database compiled into seven consecutive cohorts were used to perform this analysis. Elderly claimants aged ≥65 years were included in each cohort. To decrease potential bias between vaccinated and unvaccinated subjects, the propensity score method was applied. Logistic regression and zero-inflated negative binominal regression were used to examine the effectiveness of vaccination in preventing influenza- and pneumonia-associated outpatient visits and hospitalization.

Results

A significant decrease in both the risk and frequency of hospitalization was observed in elderly people who received influenza vaccination compared with those who did not. No similar decrease was observed in the risk and frequency of outpatient visits for influenza and pneumonia.

Conclusion

Vaccination against influenza reduced hospitalization for influenza and pneumonia in elderly Taiwanese people. These results are meaningful for the promotion of vaccination policy. Annual influenza vaccination of the elderly should be encouraged.     

Factors associated with vaccination status among Korean submariners who are eligible for free non-mandatory influenza vaccination

IntroductionSubmarine crews live in a confined setting and are vulnerable to influenza. Thus, it would be useful to identify factors that are associated with influenza vaccination. In this study, we investigated the influenza vaccination rate and the influence of health beliefs on the vaccination rate among submariners who were eligible for a free but non-mandatory vaccination program.MethodsA total of 487 Korean submariners participated in this study after the closing of a free influenza vaccination program in 2015. Data regarding the participants’ general characteristics and health beliefs (based on the health belief model [HBM]) were collected using a self-administered questionnaire, and their vaccination status was determined using their medical records. Multiple logistic regression analysis were performed to evaluate the associations of the HBM components with influenza vaccination.ResultsThe overall vaccination rate was 78% (921/1183). The unvaccinated and vaccinated respondents exhibited similar characteristics, although the vaccinated group was significantly more likely to have high-risk family members (chronic disease, age of <2 years, or age of ⩾65 years; p = 0.025). Among the HBM components, perceived severity (odds ratio: 1.38, p = 0.019) and cue to action (odds ratio: 1.74, p = 0.002) were significantly associated with a higher likelihood of influenza vaccination.ConclusionVaccination policies that emphasize the severity of influenza and prompt individuals to undergo vaccination are needed to increase the vaccination rate among people who live in confined environments or institutions with non-mandatory vaccination programs.     

台州市2018/2019年度社区老年人接种流感疫苗的保护效果

目的评估台州市2018/2019年度社区老年人接种三价灭活流感疫苗(TIV)的保护效果(VE)。方法运用前瞻性队列研究设计,招募接种和未接种TIV的≥60岁社区老年人随访6个月,观察流感样疾病(ILI)、因ILI就诊、因ILI或肺炎住院、因呼吸或循环系统疾病住院4种临床结局,计算TIV的VE。结果 TIV接种组、未接种组分别纳入研究对象1 048名、1 025名。接种TIV后1-3月预防4种临床结局的VE(95%CI)分别为-25.1(-80.4-13.2)%、-33.1(-99.2-11.1)%、35.8(-124.9-81.7)%和-12.6(-229.2-61.5)%;接种TIV后4-6月分别为25.5(-7.5-48.4)%、35.1(3.0-56.5)%、1.4(-249.1-72.1)%和-11.5(-240.9-63.5)%;接种TIV后1-6月分别为5.9(-24.2-28.7)%、11.6(-18.9-34.3)%、21.7(-99.2-69.2)%和-13.9(-155.5-49.2)%。结论台州市2018/2019年度社区老年人接种TIV对预防ILI病例发病、就诊和相关住院具有一定的保护效果。     

Factors associated with influenza vaccination among elderly persons in Southeastern Brazil

OBJECTIVE: Even though influenza vaccination is free and widely available in Brazil since 1999, coverage is still inadequate in several of the country's municipalities. The aim of the present study was to estimate vaccine coverage and to identify factors related to vaccination against influenza in the elderly population. METHODS: A household survey was carried out using a systematic random sample (N=365) of the urban population older than 60 years from the city of Botucatu, Southeastern Brazil. A logistic regression model using vaccination in 2002 as the dependent variable was used. The following covariables were tested: sex, age, socioeconomic variables (per capita income, number of persons per dormitory, schooling, marital status, occupation, time living in the city), history of morbidity and hospital admission, smoking, respiratory symptoms in last 15 days, and community activities (voluntary work, neighborhood and church activities). RESULTS: Vaccine coverage was 63.2% (95% CI: 58.3-68.2). We found a lower proportion of vaccination among the 60-64 years age group. Variables associated with vaccination in the final model were age (OR=1.09 per year; 95% CI: 1.06-1.13); arterial hypertension (OR=1.92; 95% CI: 1.18-3.13); and participation in community activities (OR=1.63; 95% CI: 1.01-2.65). With the exception of hypertension, vaccination among subjects with chronic diseases did not reach adequate levels, as expected for this high-risk group. Participation in social and community activities was associated with vaccination status. CONCLUSIONS: Socioeconomic conditions, habits, and age did not restrict access to vaccination campaigns. On the other hand, specific campaigns aimed at the 60-64 years age group may increase vaccination coverage.     

Decomposing racial/ethnic disparities in influenza vaccination among the elderly

While persistent racial/ethnic disparities in influenza vaccination have been reported among the elderly, characteristics contributing to disparities are poorly understood. This study aimed to assess characteristics associated with racial/ethnic disparities in influenza vaccination using a nonlinear Oaxaca–Blinder decomposition method. We performed cross-sectional multivariable logistic regression analyses for which the dependent variable was self-reported receipt of influenza vaccine during the 2010–2011 season among community dwelling non-Hispanic African–American (AA), non-Hispanic White (W), English-speaking Hispanic (EH) and Spanish-speaking Hispanic (SH) elderly, enrolled in the 2011 Medicare Current Beneficiary Survey (MCBS) (un-weighted/weighted N = 6,095/19.2million). Using the nonlinear Oaxaca–Blinder decomposition method, we assessed the relative contribution of seventeen covariates – including socio-demographic characteristics, health status, insurance, access, preference regarding healthcare, and geographic regions – to disparities in influenza vaccination. Unadjusted racial/ethnic disparities in influenza vaccination were 14.1 percentage points (pp) (W–AA disparity, p < 0.001), 25.7 pp (W–SH disparity, p < 0.001) and 0.6 pp (W–EH disparity, p > .8). The Oaxaca–Blinder decomposition method estimated that the unadjusted W–AA and W–SH disparities in vaccination could be reduced by only 45% even if AA and SH groups become equivalent to Whites in all covariates in multivariable regression models. The remaining 55% of disparities were attributed to (a) racial/ethnic differences in the estimated coefficients (e.g., odds ratios) in the regression models and (b) characteristics not included in the regression models. Our analysis found that only about 45% of racial/ethnic disparities in influenza vaccination among the elderly could be reduced by equalizing recognized characteristics among racial/ethnic groups. Future studies are needed to identify additional modifiable characteristics causing disparities in influenza vaccination.     

Influenza vaccination hesitancy and its determinants among elderly in China: A national cross-sectional study

BackgroundThe Chinese elderly face a significant threat from seasonal influenza, owing to the consistently low vaccination coverage. This study investigated the prevalence and determinants of influenza vaccination hesitancy among the Chinese elderly.MethodsIn 2019, 3849 elderly individuals from 10 provinces in China were recruited in a cross-sectional survey. Multinomial logistic regression was applied to investigate the determinants of influenza vaccination hesitancy.ResultsAmong the elderly respondents, 37.18% expressed some degree of hesitancy towards influenza vaccination: 19.28% were hesitant, and 17.90% refused influenza vaccination, including 19.28% acceptors with doubts and 17.90% refusers. Only 39.10% of the respondents considered themselves as the priority group for influenza vaccination, and 13.93% reported receiving a recommendation for vaccination from healthcare workers. Respondents with higher education levels and from urban areas had significantly higher odds of vaccine hesitancy than their counterparts. Confidence in the safety of vaccines was negatively associated with vaccine hesitancy, but confidence in vaccine efficacy had no such association. Respondents who perceived themselves as highly susceptible to influenza (AOR = 0.85; 95 %CI = 0.77–0.93) and those aware of the elderly as a priority group for influenza vaccination (AOR = 0.51; 95 %CI = 0.41–0.64) had a significantly lower odds of being refusers.ConclusionThis study found a high prevalence of hesitancy towards influenza vaccination among the Chinese elderly, especially well-educated and urban-dwelling respondents. The government should address vaccine hesitancy through culturally appropriate communication, subsidies for vaccination, and actively promoting vaccines through primary care professionals.     

Importance of vaccination habit and vaccine choice on influenza vaccination among healthy working adults

This randomized cluster trial was designed to improve workplace influenza vaccination rates using enhanced advertising, choice of vaccine type (intranasal or injectable) and an incentive. Workers aged 18–49 years were surveyed immediately following vaccination to determine factors associated with vaccination behavior and choice. The questionnaire assessed attitudes, beliefs and social support for influenza vaccine, demographics, and historical, current, and intentional vaccination behavior. Of the 2389 vaccinees, 83.3% received injectable vaccine and 16.7% received intranasal vaccine. Factors associated with previous influenza vaccination were older age, female sex, higher education and greater support for injectable vaccine (all P < .02). Current influenza vaccination with intranasal vaccine vs. injectable vaccine was associated with higher education, the study interventions, greater support for the intranasal vaccine and nasal sprays, less support of injectable vaccine, more negative attitudes about influenza vaccine, and a greater likelihood of reporting that the individual would not have been vaccinated had only injectable vaccine been offered (all P < .01). Intentional vaccine choice was most highly associated with previous vaccination behavior (P < .001). A key to long term improvements in workplace vaccination is to encourage first time influenza vaccination through interventions that include incentives, publicity and vaccine choice.     

Effectiveness of MF59-adjuvanted seasonal influenza vaccine in the elderly: A systematic review and meta-analysis

BackgroundIn the elderly, traditional influenza inactivated vaccines are often only modestly immunogenic, owing to immunosenescence. Given that adjuvantation is a means of enhancing the immune response, the trivalent inactivated vaccine adjuvanted with MF59 (MF59-TIV) was specifically designed to overcome this problem. Considering that, for ethical reasons, the absolute effectiveness of an influenza vaccine in the elderly cannot be demonstrated in placebo-controlled studies, the present study aimed to assess the effectiveness of MF59-TIV in preventing influenza-related outcomes in the elderly.MethodsWe conducted a systematic review of observational studies aimed at evaluating the effectiveness of MF59-TIV against influenza-related outcomes. Results of single studies were pooled whenever possible.ResultsOf the 1993 papers screened, 11 (6 case-control, 3 cohort and 2 prospective case-control) studies were identified. Hospitalization due to pneumonia/influenza and laboratory-confirmed influenza were reported in more than one study, while other outcomes (influenza-like illness, cardio- and cerebrovascular accidents) were investigated only by one study each. Pooled analysis of four case-control studies showed an adjusted MF59-TIV effectiveness of 51% (95% CI: 39–61%) against hospitalizations for pneumonia/influenza among community-dwelling seniors. Pooled results of the adjusted vaccine effectiveness against laboratory-confirmed influenza were also high (60.1%), although the 95% CI passed through zero (−1.3 to 84.3%). Other single community-based studies showed very high effectiveness of MF59-TIV in preventing hospitalizations for acute coronary [87% (95% CI: 35–97%)] and cerebrovascular [93% (95% CI: 52–99%)] events. MF59-TIV proved highly effective [94% (95% CI: 47–100%] in reducing influenza-like illness among institutionalized elderly. Furthermore, MF59-TIV displayed greater efficacy than non-adjuvanted vaccines in preventing hospitalizations due to pneumonia/influenza [adjusted risk ratio 0.75 (95% CI: 0.57–0.98)] and laboratory-confirmed influenza [adjusted odds ratio 0.37 (0.14–0.96)].ConclusionsOur results suggest that MF59-TIV is effective in reducing several influenza-related outcomes among the elderly, especially hospitalizations due to influenza-related complications.     

Influenza vaccination and risk of hospitalization among adults with laboratory confirmed influenza illness

Background

Influenza vaccine is moderately effective for preventing influenza illness. It is not known if vaccination reduces the risk of subsequent hospital admission among patients with vaccine failure and laboratory confirmed influenza illness.

Methods

Patients in a community cohort presenting with acute respiratory illness were prospectively enrolled and tested for influenza during 8 seasons to estimate seasonal vaccine effectiveness. Hospital admissions within 14 days after illness onset were identified for all participants aged ≥20 years with laboratory confirmed influenza. The association between vaccination and hospital admission was examined in a propensity score adjusted logistic regression model. The model was validated by examining the association between vaccination and hospital admission in participants without influenza.

Results

Influenza was identified in 1393 (28%) of 4996 participants. Sixty-two (6%) of 1020 with influenza A and 17 (5%) of 369 with influenza B were hospitalized. Vaccination was not associated with a reduced risk of hospital admission among all participants with influenza [adjusted odds ratio (aOR) = 1.08; 95% CI: 0.62, 1.88]; or among those with influenza A (aOR = 1.35; 95% CI: 0.71, 2.57) or influenza B (aOR = 0.67; 95% CI: 0.21, 2.15). Influenza vaccination was not associated with hospitalization after non-influenza respiratory illness (aOR = 1.14; 95% CI: 0.84, 1.54).

Conclusions

Influenza vaccination did not reduce the risk of subsequent hospital admission among patients with vaccine failure. These findings do not support the hypothesis that vaccination mitigates influenza illness severity.     

Prevalence of influenza vaccination and associated factors among pregnant women in Hong Kong

A total of 568 pregnant women in Hong Kong were interviewed. Of them, 85.4% had heard of influenza vaccine, 21.3% had ever been vaccinated, 3.9% self-reported receiving influenza vaccination (IV) in the 2005/2006 flu season, and 33% were inclined toward receiving IV in the coming year. Multivariate analysis showed that those who had been recommended by health care professionals to receive IV during pregnancy were more likely than others to have received IV. Other variables related to the Health Belief Model were significantly associated with having ever been vaccinated or inclined toward receiving IV in the coming year.     

我国6个省份全人群流感疫苗接种及认知情况调查

目的 了解调查地区全年龄组人群流感预防知识的认知及流感疫苗接种情况，探索影响流感疫苗接种的相关因素。方法 采用横断面调查设计，选择北京市、内蒙古自治区、上海市、广东省、云南省和甘肃省6个省份，通过12320卫生热线采用随机数字表拨打电话的抽样方法，于2018年3-5月开展全年龄组人群的流感防控知识、流感疫苗接种情况的电话调查，调查估计样本量为9 438人。结果 本调查应答率为46.4%（10 045/21 658），10 045名调查对象中，"流感和普通感冒有区别"的知晓率为75.3%（7 564/10 045），"流感病毒会引起严重后果"的知晓率为82.0%（8 241/10 045）。出现流感样症状后采取频繁洗手、戴口罩和自我隔离的健康行为率分别为80.4%（7 936/9 873）、75.8%（7 506/9 899）和73.6%（7 228/9 822）。最近1年流感疫苗接种率为5.7%（570/10 037）。最近1年流感疫苗接种率的相关多因素logistic回归分析结果显示，调查对象来自甘肃省或北京市、职业是医务人员或全日制学生、调查对象共同居住人数≥ 2人、出现流感样症状后戴口罩，最近1年流感疫苗接种率相对较高。结论 6个省份调查对象流感相关知识的知晓率、出现流感相关症状后的健康行为率和最近1年流感疫苗接种率均有待进一步提高。应加强流感预防知识和疫苗接种的健康教育，探索流感疫苗免费接种策略。     

Characterization of antibody responses to annual influenza vaccination over four years in a healthy elderly population

The effects of yearly influenza immunization on the level of antibody responses were assessed in 92 healthy elderly subjects immunized over four contiguous years (1993–1996) with a trivalent influenza vaccine that included A/Texas annually. Anti-A/Texas antibodies increased significantly and similarly post-vaccination each year, but returned to comparable baseline levels annually. Percentages of subjects with anti-A/Texas titers ≥40 post-vaccination were comparable over four years. Importantly, post-vaccination titers ≥40 to A/Texas in 1993–1994 predicted anti-A/Texas titers ≥40 in subsequent years. Thirty percent of individuals produced four-fold rises to any vaccine component the first year it was included in the vaccine, however, this percentage decreased to about 10% after subsequent vaccination with the same component. This study clearly supports the concept that annual immunization with the same influenza vaccine component over multiple years does not significantly decrease antibody titers in a healthy elderly population.