Coverage rates of influenza vaccination in France: a population-based cross-sectional analysis of seasons 2001-2002 and 2002-2003

INTRODUCTION: Influenza is a serious health problem in Europe. Vaccination is the only preventive measure, reducing mortality and morbidity of influenza in all age groups. OBJECTIVES: The authors had for aim to assess influenza vaccination coverage during two seasons in France, to understand the incentives and barriers to vaccination and to determine vaccination intentions for the following winter. METHODS: A random-sampling, mail-based household survey was made among non-institutionalised individuals aged 15 and over. The surveys for 2001-2002 and 2002-2003 used the same questionnaire and were subsequently pooled. Three target groups were determined for analysis: (1) persons aged 65 and over; (2) people working in the medical field and (3) persons aged 65 and over or working in the medical field. RESULTS: Influenza vaccination coverage in France decreased from 23.0% in 2001-2002 to 22.4% in 2002-2003. Most frequent reasons for being vaccinated were advice from the family doctor (50.8%), influenza considered as a serious illness (45.3%) and free vaccine (44.1%). Reasons for not being vaccinated mentioned by people who had never been vaccinated were young age (27.0%), not considering vaccination (18.9%), and not expecting to catch influenza (13.9%). CONCLUSION: Vaccination coverage decreased during the 2002-2003 season in comparison to the 2001-2002 season. The family doctor is the most important source of encouragement for people to be vaccinated against influenza. We therefore suggest that family doctors be better informed on influenza vaccine and the disease itself, so that they can actively inform their patients on these topics.     

Influenza vaccine uptake in adults aged 50-64 years: policy and practice in England 2003/2004

A small national study was carried out in England in 2003/2004 to ascertain the views of primary care trusts (PCTs) and general practitioners (GPs) on whether influenza immunisation should be extended to all people aged 50-64 years from the current recommendation of 65 years or more. Results showed that as many primary care trusts would be in favour, as would not be in favour. A similarly divided view was expressed by general practitioners. Vaccine uptake rates for high-risk (HR) and low-risk (LR) adults aged 50-64 years in the study population were higher in those practices where the GP was in favour of a more inclusive policy of offering flu vaccine to all persons aged 50 years or more, compared with those that did not favour this policy (60% versus 54% HR (p=0.02) and 16% versus 11% LR (p=0.02)). Higher rates of vaccine uptake for low-risk patients aged 50-64 years were also reported from practices where GPs perceived a greater health benefit of immunisation for this age group. Although policy for recommending vaccine to all patients aged 50 years or more is established elsewhere, opinion on whether such a policy should be adopted in England is currently divided amongst those providing local health services.     

The cost-effectiveness of a universal influenza vaccination program for adults aged 50-64 years in Australia

Currently the Australian government funds universal influenza vaccine for all those aged > or =65 years under the National Immunisation Program (NIP). Annual vaccination rates in those aged 50-64 years are significantly lower than vaccination rates in those aged > or =65 years, and currently less than half those at high-risk of influenza-related complications aged 50-64 years are immunised. This study used a decision tree model to examine the cost-effectiveness of lowering the age threshold for the influenza NIP in Australia to include those aged 50-64 years. From a healthcare payer perspective, a new influenza vaccination policy would cost $8908/QALY gained. From a societal perspective, a new influenza vaccination policy would cost $8338/QALY gained. From a governmental perspective, a new influenza vaccination policy would cost $22,408/QALY gained. The most influential parameters in deterministic sensitivity analysis included: probability of death due to influenza, vaccine efficacy against mortality, vaccine uptake, vaccine cost, and vaccine administration cost. Influenza vaccination for people aged 50-64 years appears highly cost-effective, and should be a strong candidate for funding under the NIP.     

Influenza vaccine uptake in the elderly population: Individual and general practitioner’s determinants in Central Italy,Lazio region, 2016–2017 season

BackgroundElderly people are a priority target group for influenza vaccination and their decision to be vaccinated might partly depend on advice received from general practitioners (GP). This study aims to investigate the association between influenza vaccine uptake in the elderly residents in the Lazio region of Italy and the demographic and professional characteristics of their GPs, taking simultaneously into account the elderly’s individual characteristics.MethodsWe used data retrieved from different administrative sources to retrospectively analyse the cohort of 1,255,657 elderly residents aged ≥65 years who were alive and registered in the regional healthcare service at the beginning of the 2016–2017 influenza vaccination campaign (1 Oct. 2016–31 Jan. 2017). We assessed influenza vaccine uptake at the end of the vaccination campaign and evaluated its association with both individual and GP-related characteristics through a multilevel Poisson regression models accounting for clustering at physician level.ResultsOverall, vaccination coverage at the end of vaccination campaign was 50.6%. Elderly residents who were male, older, vaccinated in the previous seasons, living in smaller provinces, and spending more money for specialist medical care showed a significantly increased probability to be vaccinated. Vaccine uptake was also significantly higher in the elderly residents assisted by GPs who got master’s degree more recently, assisted a relatively high proportion of elderly patients, received influenza vaccination, had a computer assistant, and were associated with other physicians.ConclusionsOur results indicate that influenza vaccination coverage in the elderly residents of the Lazio region is still unsatisfactorily low. We identified several determinants of influenza vaccine uptake, related to both individual and GP characteristics. Understanding how GP characteristics affected influenza vaccine uptake in the elderly population might provide insight on GPs’ attitudes and concerns regarding influenza vaccination, allowing the implementation of targeted evidence-based interventions to sensitise GPs and increase vaccination coverage.     

State-specific influenza vaccination coverage among adults aged > or =18 years--United States, 2003-04 and 2005-06 influenza seasons

Influenza epidemics occur seasonally and result in substantial morbidity and mortality among adults in the United States. Adult groups included in the 2007 Advisory Committee on Immunization Practices (ACIP) recommendation for annual influenza vaccination are persons aged 18-49 years with high-risk conditions (i.e., conditions associated with an increased risk for complications from influenza), persons aged > or =50 years, health-care personnel, and others who are household contacts or caregivers of persons at high risk (e.g., persons with high-risk conditions or children aged < or =59 months). In addition, adults who want to reduce the risk for becoming ill with influenza or of transmitting influenza to others should be vaccinated. Healthy People 2010 (HP2010) objectives include increasing vaccination levels to 90% for adults aged > or =65 years (objective 14-29a) and 60% for persons aged 18-64 years who have one or more high-risk conditions (objective 14-29c). From the 1992-93 through 2003-04 influenza seasons, seasonal influenza vaccination coverage estimates (based on Behavioral Risk Factor Surveillance System [BRFSS] data) among adults aged > or =65 years trended upward, except for three seasons (1997-98, 1999-00, and 2000-01) when no increases occurred (Figure). To evaluate recent state-specific progress toward the HP2010 objectives, CDC compared data from the 2004 and 2006 BRFSS surveys, which reflected vaccinations received during the 2003-04 and 2005-06 influenza seasons; data from the 2004-05 influenza season, which have been published previously, were not included in this comparison because that season was marked by a substantial shortage of influenza vaccine. This report describes the results of the analysis, which indicated that influenza vaccination coverage for the 2005-06 season did not return to levels observed before the vaccine shortage of 2004-05 and remained substantially below HP2010 targets. Comprehensive measures are needed to improve influenza vaccination coverage among adult populations in the United States, including increasing adoption of recommended adult immunization practices by health-care providers, raising public awareness about influenza vaccination, vaccinating throughout the influenza season, and ensuring stable supplies of readily available vaccine.     

Achieving national influenza vaccine targets--an investigation of the factors affecting influenza vaccine uptake in older people and people with diabetes

A survey by postal questionnaire of a random sample of community residents with diabetes mellitus and those aged 75 years was undertaken in one Health Authority area to examine the factors associated with influenza vaccine uptake in these groups. The questionnaire sought: information on vaccine uptake and non-uptake over the previous three winter periods; patient attitudes to and knowledge about influenza and influenza vaccine; sources of patients' information; and patients' views on improving vaccine uptake. Self-reported vaccine uptake had increased in people with diabetes from 53.9% in 1997-98 to 67.6% in 1999-2000, and in people aged 75 years and over from 63.5% in 1997-98 to 70.2% in 1999-2000. Factors significantly associated with vaccine uptake in people with diabetes included a history of previous vaccination OR 40 (95% confidence interval 9,206), recommendation by a health professional OR 14 (2.9, 90) and belief that the vaccine protects against flu OR 5.6 (1.8, 18.9). Factors significantly associated with vaccine uptake in older people included the belief that the vaccine protects against flu OR 23 (8.4, 69.4), a history of previous vaccination OR 10 (3.9, 28.3) and not being concerned about side-effects OR 4 (2.1, 7.9). Information given by a health professional was the only source of information found to significantly influence vaccine uptake. Interventions suggested to increase uptake include provision of more information and better access to influenza vaccination. It is concluded that uptake rates for influenza vaccine have increased over the last three years to 67.4% in people with diabetes and 70.2% in people aged 75 and over. Professionals play a key role in influencing the decision to have influenza vaccine. Information about influenza and its vaccine needs to be combined with improvements in service provision if overall target uptake rates of 70% (65% in those aged 65 years and over) are to be achieved.     

Influenza vaccination coverage among persons aged 50-64 years enrolled in commercial managed health-care plans--United States, 2003-04 and 2004-05 influenza seasons

To combat an unexpected shortage of influenza vaccine in the fall of 2004, CDC issued guidance to direct available vaccine supplies to persons in designated priority groups (e.g., persons aged >/=65 years, persons with certain health conditions, health-care workers, and close contacts of persons at high risk for complications from influenza). Analyses of influenza vaccination coverage for the 2004-05 influenza season indicated that coverage levels for adults in priority groups nearly reached the levels of previous years, whereas coverage levels among adults not in priority groups were approximately half the levels of the 2003-04 season. These findings suggested that national public health actions to direct available vaccine supply to persons at high risk for complications from influenza during the supply disruption were successful. To assess influenza vaccination coverage among persons aged 50-64 years for the 2004-05 influenza season relative to the 2003-04 season and to estimate the effect of shortages on selected subgroups, the National Committee for Quality Assurance (NCQA) analyzed data from a survey of persons enrolled in commercial managed care health plans. This report summarizes the findings of that analysis, which indicated that, although vaccination coverage declined substantially from 2003-04 to 2004-05 among all subgroups in this age range, respondents who were older or who reported poorer health status exhibited smaller relative declines in vaccination coverage between the two seasons.     

Influenza vaccine uptake and distribution in England and Wales using data from the General Practice Research Database, 1989/90-2003/04

BACKGROUND: Routinely collected data from patients registered with general practices participating in the General Practice Research Database (GPRD) were used to analyse influenza vaccine uptake and distribution in England and Wales between 1989/90 and 1996/97. Major changes to influenza immunization policy were introduced in 1998 and 2000 when immunization of the elderly became age related rather than risk related. This new study examines trends in vaccine uptake for high- and low-risk patients and the impact of the policy changes on uptake in the elderly. METHODS: Between 0.5 and 2.7 million patients registered with practices participating in the GPRD from 1989 to 2004 were included. Data were examined by age group, medical risk group and evidence of vaccination per study year. RESULTS: Vaccine uptake among high-risk persons aged 65 or more increased from 36.7 per cent in 1989/90 to 72.1 per cent in 2003/04. For the same period, uptake rates for high-risk persons under 65 years increased from 10.8 to 24.3 per cent. For those at high risk, uptake by females was higher in all age groups up to 65 years. Of those that were vaccinated, a higher proportion of the 65 and over were vaccinated in October each year compared with the high risk under 65 (p < 0.001). CONCLUSIONS: Coverage among high-risk patients in younger age groups continues to fall well below satisfactory levels, especially among the youngest groups. Government policy should now focus on ways to improve uptake in these patients.     

Why do older people not get immunised against influenza? A community survey

Many older people who would benefit from influenza vaccine do not get immunised. We carried out a postal questionnaire survey of people aged 65 years and over living in the community to explore views about influenza vaccine and identify ways of improving uptake. Completed questionnaires were returned by 1468/2553 (57.5%). Vaccine coverage for 1998-1999 season was 50.5% (95% confidence interval (CI) 47.9-53.1%). Important predictor variables for non-uptake included absence of medical risk factors, perceived good health, lack of advice from a doctor or nurse, and negative views on vaccine efficacy and safety. Most people had to request vaccination, only one in five got a reminder from their general practitioner. There is scope for improving influenza vaccine coverage in older people by placing more emphasis in patient information materials on vaccine efficacy and safety and by greater use of reminders.     

Influenza and pneumococcal vaccination coverage among persons aged > or =65 years and persons aged 18-64 years with diabetes or asthma--United States, 2003

Vaccination of persons at risk for complications from influenza and pneumococcal disease is a key public health strategy for preventing associated morbidity and mortality in the United States. Risk factors include older age and medical conditions that increase the risk for complications from infections. During the 1990-1999 influenza seasons, more than 32,000 deaths each year among persons aged > or =65 years were attributed to complications from influenza infection. National health objectives for 2010 call for 90% influenza and pneumococcal vaccination coverage among noninstitutionalized persons aged > or =65 years and 60% coverage among noninstitutionalized persons aged 18-64 years who have risk factors (e.g., diabetes or asthma) for complications from infections. To estimate influenza and pneumococcal vaccination coverage among these populations, CDC analyzed data from the 2003 Behavioral Risk Factor Surveillance System (BRFSS) survey. This report summarizes the results of that analysis, which indicated that 1) influenza vaccination levels among adults aged 18-64 with diabetes or asthma, 2) pneumococcal vaccination levels among adults aged 18-64 years with diabetes, and 3) influenza and pneumococcal vaccination levels among adults aged > or =65 years all were below levels targeted in the national health objectives for 2010. Moreover, vaccination coverage levels varied among states for both vaccines and both age groups. Innovative approaches and adequate, reliable supplies of vaccine are needed to increase vaccination coverage, particularly among adults with high-risk conditions.     

Influenza vaccination coverage rates in five European countries-a population-based cross-sectional analysis of two consecutive influenza seasons

INTRODUCTION: Influenza continues to be a considerable health problem in Europe. Vaccination is the only preventive measure, reducing mortality and morbidity of influenza in all age groups. OBJECTIVES: The objective of this survey was to assess the level of influenza vaccination coverage during two consecutive influenza seasons (2002/2003 and 2003/2004) in six European countries, to understand the driving forces and barriers to vaccination and to determine vaccination intentions for the following winter. METHODS: We conducted a random-sampling, telephone-based household survey among non-institutionalised individuals representative of the population aged 14 and over. The surveys used the same questionnaire for two consecutive winters: 2002/2003 and 2003/2004 data were used for Germany, Italy, Spain and the United Kingdom. 2001/2002 and 2002/2003 data were used for France. The data were subsequently pooled. Four target groups were determined for analysis: (1) persons aged 65 and over; (2) people working in the medical field; (3) persons suffering from chronic illness and (4) a group composed of persons aged 65 and over or working in the medical field or suffering from a chronic illness. RESULTS: The overall sample consisted of 20,118 individuals. The influenza vaccination coverage rate increased from 21.3% in the first season to 23.2% in the second season. The increase in coverage is statistically significant (p=0.01). The most frequent reasons for being vaccinated given by vaccines were: influenza, considered to be a serious illness which people wanted to avoid (55.8%), having received advice from the family doctor or nurse to be vaccinated (55.2%) and not wanting to infect family and friends (36.1%). Reasons for not being vaccinated mentioned by people who have never been vaccinated were: not expecting to catch influenza (40.4%), not having considered vaccination before (33.3%) and not having received a recommendation from the family doctor to be vaccinated (27.3%). Options encouraging influenza vaccination are: recommendation by the family doctor or nurse (53.1%), more available information on the vaccine regarding efficacy and tolerance (32.1%) and more information available about the disease (26.7%). Adjusted odds ratios for target group vaccination were between 3.6 (Germany) and 13.7 (UK). Vaccination rates among healthcare workers were generally very low. Adjusted odds ratios were between 0.7 (Germany) and 1.5 (Spain). CONCLUSION: The vaccination coverage during the second season increased in comparison to the first season. The family doctor is the most important source of encouragement for people to be vaccinated against influenza. It seems that the public would be more likely to be vaccinated if they had more information on the efficacy and tolerance of the vaccine, as well as the disease. We, therefore, suggest that family doctors be better informed on influenza vaccine and the disease itself, so that they can actively inform their patients on these topics.     

Rapid assessment of influenza vaccination coverage among HMO members--northern California influenza seasons, 2001-02 through 2004-05

The Vaccine Safety Datalink (VSD) is a collaborative project involving CDC and eight health maintenance organizations (HMOs) in the United States. Computerized data on vaccination, medical outcomes, and patient demographics are collected and linked under a standard protocol at multiple HMOs. Beginning with the 2003-04 influenza season, the VSD team and one of the HMOs, Kaiser Permanente Northern California (KPNC), established an automated system for rapid detection of potentially adverse events after vaccinations among its members. During the 2004-05 influenza season, in response to the influenza vaccine shortfall and resulting prioritization of vaccine distribution, this rapid analysis system also was used to assess influenza vaccination coverage weekly among KPNC members. The results indicated that KPNC followed Advisory Committee on Immunization Practices (ACIP) prioritization guidelines by targeting influenza vaccination to children aged 6-23 months and adults aged >/=65 years. For the 2005-06 influenza season, the rapid analysis system should be expanded to include data from additional HMOs and more detailed information on vaccinees (e.g., high risk for influenza complications) to better characterize influenza vaccination coverage during the 2005-06 influenza season on a weekly basis.     

Barriers and facilitators to influenza vaccination among high-risk groups aged less than 65 years - views from general practitioners and practice nurses

OBJECTIVES: To explore the views of general practitioners and practice nurses about barriers to influenza vaccination among under 65 high-risk patients and strategies to overcome those barriers. METHODS: Focus group discussions with general practitioners and practice nurses. RESULTS: Barriers identified included: lack of awareness among patients about influenza vaccination; GP workload; poor GP motivation; lack of practice nurses; lack of patient recall systems; cost of vaccine; and lack of media campaign. Strategies proposed included: public education campaigns; free supply of vaccine; dissemination of evidence to motivate GPs; incentives to establish recall systems; and greater involvement of practice nurses in the process. CONCLUSION: Influenza vaccination has not been well accepted by people aged less than 65 years. Implementation of proposed strategies has the potential to improve the vaccination coverage. IMPLICATIONS: An improvement in influenza vaccination coverage among people less than 65 years who are in high-risk groups has the potential to reduce hospitalisation and health care costs.     

Prevalence and determinants of influenza vaccination in Australians aged 40 years and over--a national survey

OBJECTIVES: To determine influenza vaccination coverage in 2001 in Australian adults aged > or = 40 years, assess awareness of and attitudes to influenza vaccine, factors associated with vaccination, and estimate uptake of free vaccine provided to those aged > or = 65 years. METHODS: National computer-assisted telephone interview (CATI) survey in October/November 2001. RESULTS: Interviews were completed with 5,266 people aged > or = 65 and 2,415 aged 40-64 years. Thirty per cent of selected households participated. Overall, 67% of respondents believed that the vaccine was somewhat to very effective in preventing influenza. Seventy-eight per cent of those aged > or = 65 years reported influenza vaccination; 89% had received it free. Independent predictors of vaccination were: belief that influenza vaccine is effective in preventing influenza (OR=13.5, 95% CI 10.6-17.2); and the presence of chronic disease (OR=1.6, 95% CI 1.3-2.0). Overall, 24% of those aged 40-64 years were vaccinated; only 34% of those who met any of the criteria for vaccination (medical risk factor, at-risk occupation, or being Aboriginal or Torres Strait Islander) reported vaccination. CONCLUSIONS: Influenza vaccine coverage was high in those aged > or = 65 years, but coverage of those at-risk aged 40-64 years remained suboptimal. Immunisation against influenza was influenced more by beliefs about the vaccine's effectiveness and existing medical risk factors, rather than socio-demographic factors such as gender and income.     

Influenza vaccination levels among persons aged > or =65 years and among persons aged 18-64 years with high-risk conditions--United States, 2003

Influenza vaccination is an effective tool for preventing hospitalization and death among persons aged > or =65 years and among persons aged 18-64 years with medical conditions that increase the risk for influenza-related complications. Two national health objectives for 2010 are to increase influenza vaccination coverage to 90% among persons aged > or =65 years and to 60% among persons aged 18-64 years who have one or more high-risk conditions (objectives 14-29a and 14-29c, respectively). To determine influenza vaccination coverage among persons in both targeted groups, CDC analyzed data from the 2003 National Health Interview Survey (NHIS). This report summarizes the results of that analysis, which determined that influenza vaccination coverage among persons aged > or =65 years and persons aged 18-64 years with high-risk conditions remains substantially below 2010 target levels. In addition, racial/ethnic disparities in coverage levels persist in both targeted populations. To improve overall influenza vaccination coverage and reduce racial/ethnic disparities, combinations of evidence-based effective interventions should be implemented, and the influenza vaccine supply should be stabilized.     

Vaccination of special populations: Protecting the vulnerable

One of the strategic objectives of the 2011–2020 Global Vaccine Action Plan is for the benefits of immunisation to be equitably extended to all people. This approach encompasses special groups at increased risk of vaccine-preventable diseases, such as preterm infants and pregnant women, as well as those with chronic and immune-compromising medical conditions or at increased risk of disease due to immunosenescence. Despite demonstrations of effectiveness and safety, vaccine uptake in these special groups is frequently lower than expected, even in developed countries with vaccination strategies in place. For example, uptake of the influenza vaccine in pregnancy rarely exceeds 50% in developed countries and, although data are scarce, it appears that only half of preterm infants are up-to-date with routine paediatric vaccinations. Many people with chronic medical conditions or who are immunocompromised due to disease or aging are also under-vaccinated. In the US, coverage among people aged 65 years or older was 67% for the influenza vaccine in the 2014–2015 season and 55–60% for tetanus and pneumococcal vaccines in 2013, while the coverage rate for herpes zoster vaccination among those aged 60 years or older was only 24%. In most other countries, rates are far lower. Reasons for under-vaccination of special groups include fear of adverse outcomes or illness caused by the vaccine, the inconvenience (and in some settings, cost) of vaccination and lack of awareness of the need for vaccination or national recommendations. There is also evidence that healthcare providers’ attitudes towards vaccination are among the most important influences on the decision to vaccinate. It is clear that physicians’ adherence to recommendations needs to be improved, particularly where patients receive care from multiple subspecialists and receive little or no care from primary care providers.     

A multi-country investigation of influenza vaccine coverage in pregnant individuals, 2010–2016

BackgroundMany countries recommend influenza vaccination during pregnancy. Despite this recommendation, influenza vaccine among pregnant individuals remains under-utilized and uptake varies by country. Factors associated with influenza vaccine uptake during pregnancy may also vary across countries.MethodsAs members of the Pregnancy Influenza Vaccine Effectiveness Network (PREVENT), five sites from four countries (Australia, Canada, Israel, and the United States) retrospectively identified cohorts of individuals aged 18–50 years who were pregnant during pre-defined influenza seasons. Influenza vaccine coverage estimates were calculated for the 2010–11 through 2015–16 northern hemisphere and the 2012 through 2015 southern hemisphere influenza seasons, by site. Sites used electronic health records, administrative data, and immunization registries to collect information on pregnancy, health history, demographics, and vaccination status. Each season, vaccination coverage was calculated as the percentage of individuals who received influenza vaccine among the individuals in the cohort that season. Characteristics were compared between those vaccinated and unvaccinated, by site.ResultsMore than two million pregnancies were identified over the study period. Influenza vaccination coverage ranged from 5% to 58% across sites and seasons. Coverage increased consistently over the study period at three of the five sites (Western Australia, Alberta, and Israel), and was highest in all seasons at the United States study site (39–58%). Associations with vaccination varied by country and across seasons; where available, parity >0, presence of a high-risk medical condition, and urban residence were consistently associated with increased likelihood of vaccination.ConclusionsThough increasing, uptake of influenza vaccine among pregnant individuals remains lower than recommended. Coverage varied substantially by country, suggesting an ongoing need for targeted strategies to improve influenza vaccine uptake in this population.     

Coverage rates of influenza vaccine in Italy during the 2002/3 and 2003/04 seasons: a cross-sectional study

The objective of this survey was to assess the level of influenza vaccination coverage in the season 2002/ 2003 compared with the season 2003/2004 in Italy, to understand the drivers and barriers to vaccination and to determine the intention for vaccination for the following winter. We conducted a random-sampling, telephone-based household survey among non-institutionalised individuals representative of the population aged 14 years and above. The surveys for 2002/2003 and 2003/2004 used the same questionnaire and were subsequently pooled. Four target groups were determined for analysis: (1) persons aged 65 years and above; (2) people working in the medical field; (3) persons suffering from a chronic illness and (4) all other groups. The overall sample consisted of 4010 people. The influenza vaccination coverage rate in Italy increased from 19.6% in season 2002/2003 to 22.2% in season 2003/2004. The most frequent reasons mentioned by vaccinees to get vaccinated were advice received from the family doctor or nurse (48.9%), influenza being considered a serious illness which people did not want to contract (38.5%) and not wanting to pass the influenza bug to family and friends (29.2%). Reasons mentioned by never vaccinated people for not getting vaccinated were the fact that people did not consider it before (34.9%), the opinion that one was not very likely to catch influenza (32.2%) and influenza not being a serious illness (23.4%). Options encouraging an influenza vaccination are a recommendation by the family doctor or nurse (58.4%), more available information on the vaccine regarding efficacy and tolerance (34.4%) and more available information on the disease (24.3%). We therefore suggest that family doctors be better informed on influenza vaccine and the disease itself in order to enable them to actively inform their patients on these topics accordingly.     

Effectiveness of repeated influenza vaccination among the elderly population with high annual vaccine uptake rates during the three consecutive A/H3N2 epidemics

BackgroundAnnually, about 80% of the Korean elderly aged ≥65 years receive influenza vaccination. Repeated annual vaccination has been suggested as an important factor of poor influenza vaccine effectiveness (VE), though reported conflicting results.MethodsDuring the consecutive A/H3N2-dominant influenza seasons between 2012 and 2015, we comparatively evaluated the VE (repeated vs. current season only) against laboratory-confirmed influenza, pneumonia and hospitalization in the elderly aged ≥65 years with influenza-like illness (ILI). Clinical and demographic data were collected prospectively, and vaccination status of prior and current seasons was verified using the immunization registry data of Korean Centers for Disease Control and Prevention.ResultsDuring the first A/H3N2-dominant season in 2012–2013, influenza vaccine showed statistically significant effectiveness against influenza A infection only and when vaccinated in the current season only (VE 53%, 95% CI 15–77). In the latter two seasons (2013–2015 years), the adjusted VE for influenza A was indistinguishable between repeated vaccination and vaccination in the current season only.ConclusionDuring consecutive influenza A/H3N2 epidemics, poor influenza vaccine effectiveness may be more pronounced among the elderly population with a high annual vaccine uptake rate.