[Effectiveness of influenza vaccination in healthy adults--a fourfold decrease in influenza morbidity during one influenza season]

Abstract

Introduction: Despite the existence and availability of effective and safe influenza vaccines, influenza still remains an important cause of morbidity and mortality worldwide, incl. all economic consequences and the increased number of days of work incapacity. Vaccination against influenza is an effective method of prevention of the disease and its complications. Nevertheless many people still do not trust the effectiveness of anti-influenza vaccination, incl. many physicians, nurses and other health professionals. The objective of the present study is to evaluate the effectiveness of vaccination against influenza in healthy adults aged 18-60 years, vaccinated with one of the five commonly available vaccines. The evaluation is based on notifications of influenza and influenza--like diseases.

Method: The trial comprised 375 subjects vaccinated against influenza during a given season, as a control group served 340 non-vaccinated subjects. Both groups of volunteers were investigated for six months. During this period the incidence of influenza or influenza--like diseases was recorded, the presence of local and general influenza symptoms, the number of days of work incapacity and the number of visits to the doctor. These data were obtained by the postal correspondence method.

Results: In the group of 375 vaccinated subjects 17 (4.5%) became ill. In the group of non-vaccinated subjects 65 (19.1%) became ill. The difference in the incidence of influenza was statistically significant. In subjects vaccinated against influenza a 73-76% effectiveness of vaccination was achieved. Subjects in the non-vaccinated group reported more than a fourfold incidence of influenza as compared with vaccinated subjects. The symptoms of the disease did not differ significantly in the two groups. The most frequent symptom of the disease which was recorded in both groups was fever higher than 38 degrees C, pain in the joints, myalgia and finally cough. More than two thirds of the sick volunteers visited their doctor while ill.

Conclusion: From the results of the study it is obvious that vaccination against influenza in healthy adults significantly reduces the incidence of influenza, reduces the number of days of work incapacity and leads to a diminution of the number of medical examinations. Vaccination against influenza is effective in the prevention of the disease and is beneficial also for healthy non-risk population groups.