The effects of influenza vaccination

ABSTRACT

BACKGROUND:Influenza is a respiratory infectious disease with high morbidity and relatively high mortality which occurs every winter. Therefore, influenza vaccination is recommended annually for high risk groups. However, the vaccination rate is not very high. It is well known that influenza vaccination prevents influenza, and some reports show partial preventive effects for the common cold. Therefore, the authors implemented this study to find out the preventive effects of influenza vaccination for influenza and the common cold. METHODS: The study period was six months from October 1997 to March 1998, and the subjects were chosen from those who visited seven Family Practice Clinics and two Family Practice Outpatient Departments of University Hospital. The vaccination group composed of those who received influenza vaccination during the period and the control group was those who did not receive the vaccination with age difference +/-3 years and of same gender. The study was done by a survey questionnaire. The data were analyzed using SPSS version 8.0 and chisquare test, t-test, and logistic regression was implemented RESULTS: The number of vaccination group was 223, the number of control group was 214, and the total subjects were 437 persons. Influenza occurred in 4 persons(1.8%) for the vaccination group, and 12 persons(5.6%) for the control group which showed significant difference(p=0.032). The common cold occurred in 69.1% of vaccination group and in 71.0% of control group with no difference. However, the duration of the common cold was 6.0 days for the vaccination group which was slightly shorter than 7.5 days for the control group(p=0.088), and the frequency of the common cold was 1.49 times for the vaccination group and 1.84 times for the control group(p=0.033). Logistic regression analysis showed that the relative risk of influenza for the vaccination group was 0.261(p=0.032), which meant 73.9% protective effect for influenza, but not for the common cold. CONCLUSIONS: Influenza vaccination can protect people from influenza, but did not protect them from common cold. However, it can lessen the frequency and duration of the common cold.