Macroepidemiology of Influenza Vaccination (MIV) Study Group. The macro-epidemiology of influenza vaccination in 56 countries, 1997--2003

Estimates of influenza vaccination target population sizes in Spain for the 2006-2007 season

This study sought to estimate influenza vaccination target population sizes in Spain for the 2006-2007 season, based firstly on current vaccine recommendations, and secondly, on the hypothetical assumption that Advisory Committee on Immunization Practices (ACIP) recommendations were to be implemented. We estimate that under present Spanish guidelines, 41% of the population should be vaccinated against influenza in the 2006-2007 season. Of those eligible for vaccination, 41% are aged >or=65 years, 16% are aged <65 years and suffer from a chronic condition, and 36% are healthy household contacts aged <65 years. If the ACIP recommendations were implemented in Spain, the target population size would increase to 26,761,506 persons (61%), and of those eligible for vaccination, 57% would fall within the age-based recommendations (ages 6-59 months or >or=50 years), 29% would come under the healthy household contacts category, and only 5% would qualify due to suffering from a medical condition. We thus conclude that approximately 18 million persons, 41% of the Spanish population, should receive influenza vaccination in the 2006-2007 season under present Spanish guidelines. With the estimated number of doses to be distributed during this season (10 million), compliance with current recommendations would amount to only 56% at best. Extending universal vaccination to the 50-64 age group should be considered as an option for improving influenza vaccination coverage, particularly among high-risk patients, because a greater proportion of persons would receive the recommended dose by becoming eligible for the more effective age-based strategies.

Impact of influenza vaccination on major cause-specific mortality

The efficacy of influenza vaccination is not well understood for major cause-specific mortality except pneumonia. For 10 months we followed the mortality data of 35,637 vaccinated elderly (>65 years old) in a county with 102,698 elderly in southern Taiwan. A multivariate Cox model showed that vaccination was significantly associated with lower mortality for all causes, [hazards ratio (HR)=0.56], stroke (HR=0.35), renal disease (HR=0.40), diabetes mellitus (HR=0.45), pneumonia (HR=0.47), COPD (HR=0.55), malignancy (HR=0.74), and heart diseases (HR=0.78), p<0.05. Influenza vaccination was strongly associated with reducing major cause-specific mortality.

Influenza vaccination: the paediatric perspective

Influenza in young children represents a significant problem to families and to society, as this population is most susceptible to developing complications and is also a major route of disease spread within communities. However, there is a paucity of European data for the burden of disease in children and the health benefits and cost-effectiveness of vaccination, leading to a lack of awareness by governments, authorities, healthcare professionals and parents. The experience in elderly individuals and the paediatric experience in the US may provide some guidance in developing studies that will provide evidence for the creation of guidelines and educational strategies within Europe.

Influenza work on the regional level in Sweden: an integrated program for vaccination of risk groups, surveillance and pandemic planning which focuses on the role of the health care worker

The aim of the study was to increase the vaccination rates of influenza among the risk groups in Region Västra Götaland, Sweden. The main interventions performed were education of doctors and nurses, information on the Internet and advice on administrative routines and organisation for the task. There was no campaign towards the risk group and no reimbursement. The vaccination rate increased from 33.6 to 54.6% in the Göteborg area between 1999 and 2004 and from 44.1 to 51.9% in the whole region. Vaccination rates increased with age and chronic disease in the elderly population, among person's 20-64 years of age with chronic disease only 23.8-34.0% were vaccinated. In order to increase the vaccination coverage in persons with chronic disease the program intensified the education of hospital staff. It was then evident that the awareness and knowledge about influenza and vaccination was limited among hospital doctors. The study demonstrates the key role of health care workers in a vaccination program and points at the importance of preparing the personnel for a pandemic situation. Co-ordination of the vaccination program with the surveillance and pandemic planning are effective means of strengthening the preventive work against influenza.

Influenza-associated hospitalization in a subtropical city

BACKGROUND

The impact of influenza on morbidity and hospitalization in the tropics and subtropics is poorly quantified. Uniquely, the Hong Kong Special Administrative Region has computerized hospital discharge diagnoses on 95% of total bed days, allowing disease burden for a well-defined population to be accurately assessed.

METHODS AND FINDINGS

Influenza-associated morbidity and hospitalization was assessed by Poisson regression models for weekly counts of hospitalizations in Hong Kong during 1996 to 2000, using proportions of positive influenza types A (H1N1 and H3N2) and B isolations in specimens sent for laboratory diagnosis as measures of influenza virus circulation. We adjusted for annual trend, seasonality, temperature, and relative humidity, as well as respiratory syncytial virus circulation. We found that influenza was significantly associated with hospitalization for acute respiratory disease (International Classification of Diseases version 9 codes [ICD9] 460-466 and 480-487) and its subcategory pneumonia and influenza (ICD9 480-487) for all age groups. The annual rates of excess hospitalization per 100,000 population for acute respiratory diseases for the age groups 0-14, 15-39, 40-64, 65-74, and 75+ were 163.3 (95% confidence interval [CI], 135-190), 6.0 (95% CI, 2.7-8.9), 14.9 (95% CI, 10.7-18.8), 83.8 (95% CI, 61.2-104.2), and 266 (95% CI, 198.7-330.2), respectively. Influenza was also associated with hospitalization for cerebrovascular disease (ICD9 430-438) for those aged over 75 y (55.4; 95% CI, 23.1-87.8); ischemic heart disease (ICD9 410-414) for the age group 40-64 y (5.3; 95% CI, 0.5-9.5) and over 75 y (56.4; 95% CI, 21.1-93.4); and diabetes mellitus (ICD9 250) for all age groups older than 40 y.

CONCLUSIONS

Influenza has a major impact on hospitalization due to cardio-respiratory diseases as well as on cerebrovascular disease, ischemic heart disease, and diabetes mellitus in the tropics and subtropics. Better utilization of influenza vaccine during annual epidemics in the tropics will enhance global vaccine production capacity and allow for better preparedness to meet the surge in demand that is inevitable in confronting a pandemic.

Influenza vaccination among cardiovascular disease sufferers in Spain: related factors and trend, 1993-2003

Based on data drawn from the 1993 and 2003 National Health Surveys (NHS), we sought to: estimate influenza vaccination coverages among Spanish cardiovascular disease (CVD) sufferers; study which variables were associated with the likelihood of being vaccinated; analyze the time-trend in coverage for the period 1993-2003. For study purposes, a CVD sufferer was defined as any adult who reported suffering from high blood pressure and/or heart disease. The proportion of vaccinated adult CVD sufferers in 1993 and 2003 totalled 39.96% and 51.73%, respectively. The following variables increased the likelihood of being vaccinated: higher age; male gender; presence of respiratory chronic diseases; non-smoker status. Coverages for CVD sufferers had improved significantly from 1993 to 2003 but still remain below desirable levels. The improvement over time is mainly due to the subgroup aged >64 years. Strategies must be implemented to improve the use of influenza vaccine among CVD sufferers in Spain in general, and among the younger age-groups in particular.

Preparing for the next influenza pandemic: lessons from multinational data

BACKGROUND

In the past decade, avian influenza has made several incursions of increasing scope and virulence into humans. The likelihood of another pandemic is increasing with time. In work recently published, influenza was found to be the principal cause of the increase in mortality in the United States during the winter months. In a companion report, the U.S. national vaccination program was shown to have increased coverage of high risk groups 5-fold from 1980 to 1999, but excess mortality did not decline in any elderly age group. The Multinational Influenza Seasonal Mortality Study has assembled and has begun to mine mortality data from many countries. Early results indicate that the U.S. results extend to other economically developed countries and probably worldwide.

RESULTS

The Multinational Influenza Seasonal Mortality Study data extend the observations of others that there were heralding events that provided advance warning for all of the pandemics of the 20th century. Moreover, in the first year of emergence of A(H3N2) viruses, the 1968-1969 pandemic produced little excess mortality outside of North America. It appears that there were at least 2 variants of the pandemic virus, differing at 1 or more internal gene loci, and that the more virulent form emerged as dominant in the second pandemic season.

CONCLUSIONS

Integrating these findings, it seems clear that the influenza control strategy now used in about 50 countries is less than optimal. While it is likely that there will be more time to react in the pandemic season than previously imagined, an enhancement of the historical strategy is clearly indicated. Furthermore, the vaccine shortage that is presently inevitable suggests that a departure from the historical strategy if calamitous ineffectiveness is to be avoided.