Evolution of influenza vaccination coverage in France from 2001 to 2006

INTRODUCTION: The increased risk of a new influenza pandemic has raised awareness of the need for high influenza vaccination rates. OBJECTIVES: This study aims at assessing trends in influenza vaccination coverage from 2001 to 2006 in France, at understanding the drivers and barriers, and to identify vaccination intentions for 2006/2007. METHODS: We conducted a mail-based household survey on 9,835 persons representative of the population from age 15. Essentially, the same questionnaire was used in all seasons. RESULTS: The influenza vaccination coverage rate slightly increased, reaching 24.2% in 2005/2006 (70.1% in patients over 65). In the last two seasons the fact that the vaccination was provided for free was the most frequent reason for getting vaccinated. Older age, considering influenza as a serious disease and recommendations from the family doctor or nurse were also important drivers for vaccination. Only 2% of those vaccinated in 2005/2006 indicated the threat of avian influenza as a reason. The reasons for non-vaccination among persons never vaccinated before were feeling too young for vaccination, never having considered vaccination before and absence of recommendation by the family doctor. Among those who were previously vaccinated but not in the current season, the reasons for not being vaccinated were not finding vaccination necessary, forgetfulness and having influenza-like illness despite vaccination. CONCLUSION: Stable vaccination rates were observed from 2001 to 2006. France is well on its way to reach the international vaccination goal set by the WHO (75% in the elderly population), but continuously effort is needed for others.     

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 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.     

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.     

Compliance with influenza and pneumococcal vaccinations in Israel, 1999-2002

BACKGROUND: In a previous study, we found a relatively low compliance with influenza vaccination among the elderly (65 years and over) in both 1998/1999 and 1999/2000 winters. Prior to the 2000/2001 winter season, a campaign was conducted by the Israeli Ministry of Health and the local health maintanance organizations for improving compliance with influenza and pneumococcal vaccinations. The main purpose of the present study was to monitor the impact of that campaign on compliance with influenza and pneumococcal vaccinations. OBJECTIVES: (a) To compare the compliance rate of target groups with influenza vaccination in Israel during 2000/2001 and 2001/2002 winter seasons with previous years, (b) to estimate the compliance rate of the elderly with pneumococcal vaccination in Israel in the last 5 years, (c) to determine reasons for non-compliance. METHODS: Questions about compliance with influenza and pneumococcal vaccinations were included in quarterly national telephone surveys monitoring acute morbidity in Israel. Each survey was based on a sample of about 900 households and was carried out during three successive evenings. Questions were directed at interviewees of 18 years and over who were asked to report the vaccnation status of all the household members. RESULTS: A gradual increase in compliance with influenza vaccination was demonstrated for the elderly (aged 65 years and over) in the 2000/2001 (54.4%) and 2001/2002 (60.8%) winter seasons compared to the previous two seasons (51.6% in 1998/1999 and 49.1% in 1999/2000). A slight nonsignificant increase was also observed in the 50-64 age group (18.3% in 2002 survey). The proportion of the elderly who were reported to be vaccinated against pneumonia in the five years preceding the interview was higher in the 2002 survey (27.9%) compared to that of 2001 (20.1%). Lack of physician recommendation and low degreee of risk perception seem to be the major reasons hindering the achievement of higher rates of vaccination coverage. CONCLUSION: The vaccination campaign carried out in Israel prior to the 2000/2001 winter season was moderately successful in increasing the coverage of influenza and pneumococcal vaccinations in target groups. Performing this type of campaign every year before the influenza season should contribute to improving the compliance with vaccination of target groups.     

History of influenza vaccination programs in Japan

In 1976, influenza mass vaccination among schoolchildren was started under the Preventive Vaccination Law, which was intended to control epidemics in the community. However, in the late 1980s, questions about this policy and vaccine efficacy arose, and a campaign against vaccination began. In 1994, influenza was excluded from the target diseases list in the Preventive Vaccination Law, without considering the immunization policy with respect to the common indications in high-risk groups. In 2001, the Law was again amended, specifying target groups, such as the elderly aged 65 or over, for influenza vaccination. In the 2005--2006 season, vaccine coverage among the elderly reached 52%. This shows that the need for vaccination has gradually become understood. However, the anti-vaccination campaign, which claims that the influenza vaccine has no efficacy, is still active. Vaccine efficacy studies that were not properly conducted are also being reported. In 2002, the Ministry of Health, Labor, and Welfare organized a research group on vaccine efficacy consisting of epidemiologists. The present symposium, as part of the 9th Annual Meeting of the Japanese Society for Vaccinology in 2005, was planned to further introduce epidemiological concepts useful in studying influenza vaccine efficacy.     

Characteristics associated with seasonal influenza vaccination of preschool children--Oregon, 2006-2008

Starting with the 2010-11 influenza season, the Advisory Committee on Immunization Practices (ACIP) recommended that all children aged ≥6 months be vaccinated against influenza annually, and that previously unvaccinated children aged ≤8 years be given 2 doses of vaccine. The American Academy of Pediatrics (AAP) also recommends influenza vaccinations for this population. Throughout influenza seasons, preschool children often have higher rates of influenza-related hospitalization than any other age group except older adults. To estimate influenza vaccination coverage and identify sociodemographic and health-care usage correlates of influenza vaccination status among children aged 2 years, data from the 2006-2008 Oregon Pregnancy Risk Assessment Monitoring Survey follow-back survey (Oregon PRAMS-2) were analyzed. This report summarizes the results. In Oregon, 37.7% of mothers reported that their children had received an influenza vaccination during the most recent influenza season. Factors positively associated with recent influenza vaccination in the multivariable-adjusted model were children's influenza vaccination in the previous year, children's receipt of all recommended immunizations, children's uninterrupted health insurance coverage, and mothers' unmarried status. The only factor negatively associated with vaccination was use of a family doctor rather than a pediatrician for well-child visits. The concern about vaccinations most commonly identified by mothers of children who had not received an influenza vaccination during the most recent influenza season (33.9%) was the opinion that too many shots are given at a time. This report highlights the need for health-care provider-based and community-based strategies to increase influenza vaccination coverage for children in Oregon.     

Racial and ethnic disparities in influenza vaccination coverage among adults during the 2004-2005 season

During the 2004-2005 influenza season, the supply of vaccine to the United States was significantly reduced. In response, the Centers for Disease Control and Prevention and the Advisory Committee on Immunization Practices issued interim recommendations for prioritizing vaccination. Given trends in racial/ethnic disparities in vaccination for influenza, the authors assessed the impact of the shortage on those historically less likely to be vaccinated. Using data from the Behavioral Risk Factor Surveillance System, they considered vaccination coverage among those non-Hispanic Whites, non-Hispanic Blacks, and Hispanics who had priority for being vaccinated during the 2004-2005 influenza season. The vaccine shortage had a significant negative effect on coverage among adults aged 65 years or older across the three racial/ethnic groups. Yet, the magnitude of the disparities in coverage did not change significantly from previous seasons. This finding may imply similar patterns of vaccine-seeking behavior during shortage and nonshortage years. No racial/ethnic differences were seen among adults aged 18-64 years, which likely reflects the higher percentage of health-care workers in this age group. Yearly monitoring of influenza vaccine coverage is important to assess the long-term impact of shortages on overall coverage and gaps in coverage between racial/ethnic groups.     

Influenza vaccination and self-reported reasons for not receiving influenza vaccination among Medicare beneficiaries aged > or =65 years--United States, 1991-2002

Annual influenza vaccination of the U.S. elderly population has been demonstrated as safe and effective in reducing the risks of illness, hospitalization, and death. The Medicare Current Beneficiary Survey (MCBS) has measured annual influenza vaccination rates since 1991; the latest data available are for the 2001-02 influenza season. Since 1996, self-reported reasons for not receiving influenza vaccine also have been measured. During 1991-2002, MCBS indicated a steady upward trend in vaccination coverage among Medicare beneficiaries, with the exception of the 2000-01 influenza season, when vaccine distribution was delayed. The most frequently cited reasons for not receiving influenza vaccine were 1) not knowing that influenza vaccination was needed and 2) concerns that vaccination might cause influenza or side effects. During the 2000-01 influenza season, vaccine shortage or unavailability was noted for the first time as an important reason for nonvaccination. Further efforts are needed to educate the elderly regarding the benefits of influenza vaccination and to address any concerns regarding the safety of the vaccine.     

Influenza vaccination coverage among children aged 6-59 months--six immunization information system sentinel sites, United States, 2006-07 influenza season

In June 2006, the Advisory Committee on Immunization Practices (ACIP) expanded its 2004 recommendation for routine influenza vaccination of children aged 6-23 months to include children aged 24-59 months. The 2006 ACIP recommendations also reemphasized that previously unvaccinated children aged <9 years should receive 2 doses of influenza vaccine administered at least 1 month apart to be fully vaccinated. In 2007, using data from six immunization information system (IIS) sentinel sites, CDC conducted the first assessment of influenza vaccination coverage among children aged 6-59 months during the 2006-07 influenza season. The findings demonstrated that, at all six sites, <30% of children aged 6-23 months and <20% of children aged 24-59 months were fully vaccinated. Vaccination coverage data from national and state surveys for an influenza season generally are not available until the next influenza season. Rapid assessment of influenza vaccination coverage can help direct activities of state and local public health agencies aimed at increasing the number of children fully vaccinated against influenza.     

Influenza vaccination coverage in patients with cystic fibrosis followed at 12 care centers in the Greater South Region of France for the season 2005/2006

The objective of this observational study was to estimate influenza vaccination coverage for the 2005/2006 season in cystic fibrosis (CF) patients consulting at or hospitalized in 12 CF care centers. Data from 518 CF patients >6 months of age (children: 64.9%) were analyzed: 79.9% were vaccinated. The vaccination coverage was 85.6% in children, 69.4% in adults and 44.4% in transplanted patients. General practitioners vaccinated 67.9% of the patients. "Lack of time" reason was reported by 24.7% non-vaccinated patients. In France, influenza vaccination coverage in CF patients meets the National Health objective (> or =75% by 2008), but could be improved in adults and transplanted patients.     

Exploring vaccination coverage and attitudes of health care workers towards influenza vaccine in Cyprus

Seasonal influenza is a major public health problem. Nosocomial influenza is particularly concerning as it may affect patients at high risk for complications. Unvaccinated health care workers (HCWs) are an important source of nosocomial influenza and therefore a priority target group for vaccination. Despite the fact that some European countries have high coverage rates such as UK (76.8% in season 2020/21), others continue to have low coverage rates for influenza vaccines. This study aims to estimate vaccination coverage in HCWs in Cyprus, an island country located in the Eastern Mediterranean region and describe their attitudes towards influenza vaccination.MethodsThis is a questionnaire based, nation-wide study assessing flu vaccination coverage in 2019–2020 and attitudes related to vaccination acceptance, of 962 HCWs in both public and private health care facilities. Multivariable logistic regression was used to investigate factors associated with flu vaccination status.ResultsFlu vaccination coverage was estimated as 31.8%. The top two reasons for getting vaccinated were to protect their family (81.4%) and themselves (77.4%). The top two reasons for not getting immunised, besides “no particular reason” (25.7%), included disbelief for vaccine effectiveness (21.5%) and safety (29.3%). The regression model showed that doctors compared to nurses had 10 times the odds of being vaccinated. Other factors positively associated with flu vaccination were encouragement by the supervisor, having sufficient knowledge on flu and flu vaccination and easy access to vaccination. A percentage of 54.8% of participants stated that COVID-19 pandemic strongly or somewhat influenced their decision to get vaccinated.ConclusionFlu vaccination coverage in HCWs in Cyprus is rather low, similar to some other European countries. Barriers and facilitators in this study can be considered in strategies to increase flu vaccination uptake. Such questionnaire-based surveys should be repeated in order to evaluate effectiveness of targeted vaccination campaigns.     

Influenza and pneumococcal vaccination of adults aged > or = 65: racial/ethnic differences

BACKGROUND: Influenza and pneumococcal polysaccharide vaccination (PPV) rates among persons aged > or = 65 years are significantly below national objectives of 90%, particularly among blacks and Hispanics. This study of the 2002-2003 influenza season examines factors that may be associated with low coverage. METHODS: A national sample of 1839 community-dwelling adults aged > or = 65 years was surveyed by telephone during January-May 2003. Outcomes analyzed in 2004-2005 included self-reported influenza vaccination and PPV; place of vaccination; and among the unvaccinated, main reasons for nonvaccination, awareness of vaccination, and receipt of provider recommendation for vaccination. RESULTS: Influenza vaccine coverage was 67.8%, and PPV coverage was 60%. Coverage among blacks and Hispanics was > or = 15 percentage points below that of whites. Half (52%) of persons who had not received PPV were aware it was recommended for persons their age, and < 10% had received a recent physician recommendation for PPV. Concern about side effects and not thinking that they needed the vaccine were the most frequently cited reasons for not receiving an influenza vaccination. In each racial/ethnic group, prevalence of potential missed opportunities (recent doctor visit, but no vaccine recommendation from provider and no influenza vaccination) was higher than prevalence of potential vaccine refusal (recent doctor visit and vaccine recommendation from provider, but no vaccine): blacks, 26.9% versus 7.9%; Hispanics, 19.9% versus 12.1%; and white non-Hispanics, 16.2% versus 6.1%. CONCLUSIONS: Improved adherence to vaccination guidelines by healthcare providers could substantially raise coverage in all racial/ethnic groups. Multiple factors contribute to racial/ethnic disparities, and their relative contributions should be further quantified.     

Vaccine coverage survey of the elderly in 11 Italian regions

In 2002, a sample survey of the population > or =65 years of age was conducted in 11 Italian regions that included information on the influenza, pneumococcal, and tetanus vaccination status. In each region, cluster sampling was used to select 210 individuals. In the Campania region, a separate random sample of 100 individuals was selected for Naples. Information on vaccination status was collected via an interview conducted in the participants' homes. A total of 2299 persons participated in the survey. During the 2001--2002 influenza season, 61% of the population reported that they had been vaccinated (regional range 39%-70%). The proportion of the population that had received an influenza vaccine increased with age and was higher than those with underlying diseases and conditions (70% of those > or =75 years of age with underlying problems). The percentage of those who reported having been vaccinated against tetanus was 54% (regional range 11% to 79%); coverage was higher among males and decreased with age. Only 24% of the sample reported having been adequately vaccinated (at least 3 doses, of which the last was administered during the last 10 years). Five percent had been vaccinated against pneumococcus, and none of the regions had a coverage higher than 15%. The elderly represent a segment of the population that is especially vulnerable to infectious diseases and often have problems with access to health services. These findings underline the need to improve vaccine coverage using strategies specifically targeted for this age group.     

Use of a mandatory declination form in a program for influenza vaccination of healthcare workers.

OBJECTIVE: To evaluate the utility and impact of using a declination form in the context of an influenza immunization program for healthcare workers. METHODS: A combined form for documentation of vaccination consent, medical contraindication(s) for vaccination, or vaccination declination was used during the 2006-2007 influenza season in a healthcare system employing approximately 9,200 nonphysician employees in 3 hospitals; a skilled nursing care facility; a large, multisite, faculty-practice plan; and an administrative building. Responses were entered into a database that contained files from human resources departments, which allowed correlation with job category and work location. RESULTS: The overall levels of influenza vaccination coverage of employees increased from 43% (3,892 of 9,050) during the 2005-2006 season to 66.5% (6,123 of 9,214) during the 2006-2007 season. Of 9,214 employees, 1,898 (20.6%) signed the declination statement. Among the occupation groups, nurses had the lowest rate of declining vaccination (13.2% [393 of 2,970]; P < .0001), followed by pharmacy personnel (18.1% [40 of 221]), ancillary personnel with frequent patient contact (21.9% [169 of 771), and all others (24.7% [1,296 of 5,252]). Among the employees who declined vaccination, nurses were the least likely to select the reasons "afraid of needles" (3.8% [15 of 393], vs. 9.1% [137 of 1,505] for all other groups; P < .001) and "fear of getting influenza from the vaccine" (13.5% [53 of 393], vs. 20.5% [309 of 1,505]; P = .002). Seven pregnant nurses had been advised by their obstetricians to avoid vaccination. When declination of influenza vaccination was analyzed by age, 16% of personnel (797 of 4,980) 50 years of age and older declined to be vaccinated, compared with 26% of personnel (1,101 of 4,234) younger than 50 years of age (P < .0001). CONCLUSIONS: Implementing use of the declination form during the 2006-2007 influenza season was one of several measures that led to a 55% increase in the acceptance of influenza vaccination by healthcare workers in our healthcare system. Although we cannot determine to what degree use of the declination form contributed to the increased rate of vaccination, use of this form helped the vaccination program assess the reasons for declination and will help to focus future vaccination campaigns.     

Racial/ethnic differences in influenza vaccination in the Veterans Affairs Healthcare System

BACKGROUND: Racial/ethnic differences in influenza vaccination exist among elderly adults despite nearly universal Medicare health insurance coverage. Overall influenza vaccination prevalence in the Veterans Affairs (VA) Healthcare System is higher than in the general population; however, it is not known whether racial/ethnic differences exist among older adults receiving VA healthcare. Racial/ethnic differences in influenza vaccination in VA were assessed, and barriers to and facilitators of influenza vaccination were examined among veteran outpatients aged 50 years and older. METHODS: A random sample of 121,738 veterans receiving care at VA outpatient clinics during the 2003-2004 influenza season completed the mailed Survey of Health Experiences of Patients (77% response rate). Multivariate logistic regression was used to examine associations among race/ethnicity and influenza vaccination prevalence, barriers, and facilitators. Analyses were conducted during 2005 and 2006. RESULTS: Based on unadjusted prevalences, non-Hispanic blacks, Hispanics, and American Indian/Alaskan Natives were significantly less likely to be vaccinated for influenza compared to non-Hispanic whites (71%, 79%, and 74%, respectively, vs 82%). After adjustment for age, gender, marital status, education level, employment, having a primary care provider, confidence and/trust in provider, and health status, only non-Hispanic blacks remained significantly less likely to be vaccinated compared to non-Hispanic whites (75% vs 81%). Influenza vaccination barriers and facilitators varied by race/ethnic group. CONCLUSIONS: Compared to non-Hispanic whites, non-Hispanic blacks were less likely to receive influenza vaccination in the VA healthcare system during the 2003-2004 influenza season. Although these differences were small, results suggest the need for further study and culturally informed interventions.     

Negative effect on immune response of repeated influenza vaccination and waning effectiveness in interseason for elderly people

BackgroundThrough test negative designs for visiting a doctor because of influenza-like illness, many studies have found decreasing efficacy of repeated vaccination. Furthermore, waning effectiveness during interseason periods has been reported. This study was conducted to confirm negative effects of repeated vaccination in individuals with the same vaccine strain and to measure waning effects.MethodsOur cohort includes 66 participants older than 65 years old recruited from an outpatient department of one hospital. All were vaccinated, with hemagglutination inhibition (HI) antibody titers measured from 2001/02 season through the 2003/04 season. HI antibody titers were measured three times in one season: pre-vaccination, post-vaccination, and post-epidemic. To test negative effects of immune response to the repeated vaccination, differences between protection rates and differences between response rates were analyzed for individuals in the two consecutive seasons. For the test of waning effectiveness, we measured the difference in geometric mean titers of HI antibody between post-epidemic results and pre-vaccination results obtained in the following season.ResultsProtection rates were 40–55% in A/New Caledonia/20/99 and ≥75% in A/Panama/2007/99 by repeated vaccination. In A/New Caledonia/20/99 and A/Panama/2007/99 in the 2003/04 season, significant decreases were found in protection rates from the earlier seasons, although the rate for A/Panama/2007/99 in the 2002/03 season increased significantly from that of the prior season. The respective response rates in the 2003/04 season in A/New Caledonia/20/99, and in the 2002/03 and 2003/04 seasons in A/Panama/2007/99 decreased significantly from those of earlier seasons. Regarding waning effectiveness, antibody titers for A/New Caledonia/20/99 in 2003/04 season, and A/Panama/2007/99 in 2002/03 and 2003/04 seasons decreased significantly to 37.0–66.7%.ConclusionResults show significant negative effects of immune response by repeated vaccination and show significant waning effectiveness during the interseason for individuals with the same strain of influenza type A. The proportion of elderly people with HI antibody titers of ≥1:40 might be maintained by repeated influenza vaccination.     

In a prospective observational study, influenza vaccination prevented hospitalization among older home care patients

OBJECTIVE: The aim of the study is (1) to describe the prevalence of vaccination against influenza in older home care patients and (2) to investigate the protective effect of influenza vaccination for hospitalization events. STUDY DESIGN AND SETTING: This is an observational study conducted in four large cohorts of elderly patients in home care during the 1998-1999, 1999-2000, 2000-2001, and 2001-2002 influenza seasons. We analyzed data from the Italian Silver Network Home Care project. A total of 2,201 patients were enrolled in the present study. The main outcome measures were prevalence of vaccination against influenza and the rate of hospitalization according to vaccination status and influenza season. RESULTS: The rate of influenza vaccination was around 48% of the studied sample. During the follow-up including the peak of influenza and the total influenza season, 412 subjects (40%) were hospitalized among vaccinated compared to 610 subjects (59%) among not vaccinated (P<0.001). After adjusting for age, gender, location of home care program, and all the variables significantly different between vaccinated and not-vaccinated subjects, vaccinated subjects were less likely to be hospitalized compared to not-vaccinated subjects (OR, 0.73; 95% CI 0.60-0.90). CONCLUSIONS: Vaccination against influenza has an important prognostic implication for frail geriatric patients living in the community.     

The Relationship between Influenza Vaccination and Outpatient Visits for Upper Respiratory Infection by the Elderly in Taiwan

OBJECTIVE: To evaluate the effect of influenza vaccination on the reduction of the risk of outpatient visits for upper respiratory infection (URI) among the elderly in Taiwan. METHODS: The data for this observational study, consisting of 1729 people aged 65 years or older, were drawn from Taiwan's 2001 National Health Interview Survey. This survey data was then linked with National Health Insurance claim data for December 2001 to November 2002. Survival analysis of Cox proportional hazards model was performed to examine the risk of URI outpatient visits in elderly people vaccinated with the influenza vaccine and those not vaccinated during a year-long study period since the influenza season began. To adjust for potential self-selection bias, we used propensity score method to categorize individuals into two groups, based on the predicted probability of being vaccinated from a logistic regression of spatial random effect. Propensity score group 1 (PSG 1) were those with a predicted probability of being vaccinated lower than 0.5, and PSG 2 were those with a predicted probability of being vaccinated of 0.5 or higher. RESULTS: The overall vaccination rate was 50%. Logistic regression showed the probability of being vaccinated was related to the number of outpatient visits for URI before the influenza season began (odds ratio (OR) 1.07; 95% confidence interval (CI) 1.04-1.10). Our first survival analysis showed that being vaccinated significantly reduced the risk of URI outpatient visits in PSG 2 during the 1-year study period (hazard ratio 0.89; 95% CI 0.81-0.97). Separate survival analysis showed that being vaccinated reduced the risk of URI outpatient visits for both PSG groups during the first 3 months of the study period. CONCLUSION: Being vaccinated could reduce the risk of outpatient visits for URI among the elderly during the influenza season.