[Efficacy of influenza vaccine for young children in Mie Prefecture in the 1999/2000 prevalent season].
OBJECTIVE
The purpose of this survey was to investigate the efficacy and safety of influenza HA vaccine for children between 1 and 6 years of age in Mie Prefecture during the 1999/2000 prevalent season.


METHODS
We surveyed clinical data for children aged between 1 to 6 who visited five clinics in Mie Prefecture. Dividing them into vaccinated and non-vaccinated groups, we surveyed their basic properties, disease histories and manifestation of symptoms. The survey was performed with the consent of parents who were informed of the purpose. We also surveyed the adverse effects within 48 hours after vaccination. The serum HI titers of the vaccinated children were sampled three times: before the first vaccination and after the first and second vaccinations. The data were analysed with the chi-squared test and a multiple logistic model.


RESULTS
The frequency of febrile episodes above 38 degrees C was significantly lower in the vaccinated than the non-vaccinated group. While the relative risk for the entire survey period was 0.79, it declined to 0.62 during the peak period of the epidemic. Furthermore, the odds ratio was 0.42 by the multiple logistic model. Among the vaccinated group, the pattern in the increase of HI titer after vaccination varied depending on the species of vaccine antigen. In addition, the frequency of febrile episodes above 38 degrees C was significantly lower in the group which had an HI titer to A/Sydney antigen of 1:40 or more than in these with values below 1:40.


CONCLUSIONS
The relative risk of febrile episodes above 38 degrees C during the influenza prevalent season was 0.62 or below, and vaccine efficacy was 38 percent or above. Considering the significant difference in the frequency of febrile episodes between the groups with HI titers above and below 1:40, it is necessary to study strategies for those with a low response.
Takahashi
Hiroaki
H
Mie Prefectural Science and Technology Promotion Center, Public Health and Environment Research Division.
Ohkuma
Kazuyuki
K
Teramoto
Yoshihiro
Y
Fukuta
Miwa
M
Yano
Takuya
T
Sugiyama
Akira
A
Nakayama
Osamu
O
Kamiya
Hitoshi
H
D002648:Child; D002675:Child, Preschool; D003625:Data Collection; D005260:Female; D006801:Humans; D007223:Infant; D007252:Influenza Vaccines / Q000009:adverse effects; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control*; D007564:Japan / Q000453:epidemiology; D008297:Male; D014611:Vaccination / Q000706:statistics & numerical data*
D007252:Influenza Vaccines