The predictive value of influenza symptomatology in elderly people.

OBJECTIVE: We aimed to determine the complex of symptoms which has the highest predictive value for the diagnosis of influenza. METHOD: A questionnaire study with questions regarding the symptomatology of influenza among patients aged 60 and older (n = 1838). Thirty-four participating GPs recorded the symptomatology of patients who came to their general practice with influenza-like complaints. The validity of the diagnostic conclusion of the GP, as well as the diagnostic validity of the criteria of the International Classification of Health Problems in Primary Care (ICHPPC-2) and the Sentinel Stations in The Netherlands, was determined with the help of the predictive value and odds ratio, using serologically confirmed influenza as the gold standard. The same method was used to determine which complex of symptoms has the highest predictive value for influenza. The results were verified using logistic regression analysis. RESULTS: The predictive value of the diagnostics of the GP amounted to 35%. The predictive values of the diagnostics according to the criteria of the two classification methods were 24% (Sentinel Stations) and 18% (ICHPPC-2). Of the individual symptoms, the combination of fever, coughing and acute onset had the highest predictive value (30.3%) for the diagnosis of influenza. CONCLUSION: It is recommended that the criteria of the Sentinel Stations in The Netherlands and the ICHPPC-2 be adapted in the following way: influenza is likely if, out of the entire complex of symptoms, at least fever, coughing and an acute onset occur.

[Cost-effectiveness of influenza vaccination The Netherlands]. / Kosteneffectiviteit van influenzavaccinatie in Nederland.

OBJECTIVE: To determine the cost-effectiveness of influenza vaccination of all people aged 65 or over in the Netherlands. DESIGN: Model calculations. SETTING: National Institute of Public Health and Environment, Bilthoven, the Netherlands. METHOD: The cost-effectiveness of vaccination strategies was calculated using a mathematical model, with which the epidemiological effects in terms of morbidity and mortality as well as the direct costs of care of an influenza epidemic can be determined. The cost-effectiveness of non-intervention, of the current vaccination scenario for risk groups, and of an alternative scenario involving vaccination of all persons aged 65 or over and of all younger persons in risk groups, was calculated. RESULTS: Influenza-related care (the number of GP contacts and hospital days) and related costs decreased more with the alternative than with the current risk group scenario. Although the costs of care decreased when more people were vaccinated, the cost of vaccination increased more so that total net costs rose (55 million guilders versus 24 million). In the alternative scenario yearly 1115 life years more were won than with the current practice. CONCLUSION: Vaccinating all risk groups and all persons aged 65 or more has a favourable cost-effect ratio in comparison with other preventive intervention programmes.

The efficacy of influenza vaccination in elderly individuals. A randomized double-blind placebo-controlled trial.

OBJECTIVE: To determine the efficacy of influenza vaccination in elderly people. DESIGN: Randomized double-blind placebo-controlled trial. SETTING: Fifteen family practices in the Netherlands during influenza season 1991-1992. PARTICIPANTS: A total of 1838 subjects aged 60 years or older, not known as belonging to those high-risk groups in which vaccination was previously given. INTERVENTION: Purified split-virion vaccine containing A/Singapore/6/86(H1N1), A/Beijing/353/89(H3N2), B/Beijing/1/87, and B/Panama/45/90 (n = 927) or intramuscular placebo containing physiological saline solution (n = 911). MAIN OUTCOME MEASURES: Patients presenting with influenzalike illness up to 5 months after vaccination; self-reported influenza in postal questionnaires 10 weeks and 5 months after vaccination; serological influenza (fourfold increase of antibody titer between 3 weeks and 5 months after vaccination). RESULTS: The incidence of serological influenza was 4% in the vaccine group and 9% in the placebo group (relative risk [RR], 0.50; 95% confidence interval [CI], 0.35 to 0.61). The incidences of clinical influenza were 2% and 3%, respectively (RR, 0.53; 95% CI, 0.39 to 0.73). The effect was strongest for the combination of serological and clinical influenza (RR, 0.42; 95% CI, 0.23 to 0.74). The effect was less pronounced for self-reported influenza. CONCLUSION: In the elderly, influenza vaccination may halve the incidence of serological and clinical influenza (in periods of antigenic drift).

Immune response to influenza vaccination of elderly people. A randomized double-blind placebo-controlled trial.

The objective of this study was to determine the immune response to influenza vaccination in elderly people, using a randomized, double-blind, placebo-controlled trial. Venous blood was taken from 1838 people aged 60 years and older, prior to injection with the influenza vaccine or a placebo. A second blood sample was taken three weeks later. The antibody reaction was measured by comparing the geometric mean titre and the percentage of participants who had a protective antibody titre before and after vaccination and for all sera of each strain. A protective antibody titre was found in 43-68% of those who had received the vaccine, depending on the strain investigated. Patients potentially at risk showed a response similar to the other participants. We conclude that influenza vaccination in elderly people provides a reasonable to good immune response. Research is needed on whether a good immune response decreases the incidence of influenza.

Adverse reactions to influenza vaccine in elderly people: randomised double blind placebo controlled trial.

OBJECTIVE: To assess the frequency and type of side effects after influenza vaccination in elderly people. DESIGN: Randomised double blind placebo controlled study. SETTING: 15 general practices in the southern Netherlands. SUBJECTS: 1806 patients aged 60 or older, of whom 904 received influenza vaccine and 902 placebo. MAIN OUTCOME MEASURES: Adverse reactions reported on postal questionnaire completed four weeks after vaccination. RESULTS: 210 (23%) patients given vaccine reported one or more adverse reactions compared with 127 (14%) given placebo. The frequency of local adverse reactions were 17.5% in the vaccine group and 7.3% in the placebo group (p < 0.001). There was no difference in systemic adverse reactions (11% v 9.4%; p = 0.34). In general, men reported fewer side effects than women. CONCLUSION: Only local side effects were more common in vaccinated patients and all side effects were mild.