A review of the indirect protection of younger children and the elderly through a mass influenza vaccination program in Japan

Abstract

In the past, Japan’s strategy for controlling influenza was to vaccinate schoolchildren based on the theory that this could reduce influenza epidemics in the community, and a special program to vaccinate schoolchildren against influenza was begun in 1962. However, the program was discontinued in 1994 because of lack of evidence that it had limited the spread of influenza in the community. In 2001, it was reported that a clear decrease in excess mortality had coincided with the timing of the schoolchild vaccination program. This decrease could have potentially occurred because elderly people were protected by herd immunity generated by the program. Moreover, the program protected the younger siblings of schoolchildren against influenza-associated encephalopathy. Finally, the program was effective in reducing the number of class cancellations and absenteeism from school. During the period when the program was in effect, Japanese schoolchildren served as a barrier against influenza in the community.

Keywords::

• elderly
• herd immunity
• influenza
• schoolchildren
• vaccine

Financial & competing interests disclosure

N Sugaya has received speaker’s honoraria from Daiichi Sankyo, Shionogi, Chugai and GlaxoSmithkline. The author has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

• In the past, Japan’s strategy for controlling influenza was to vaccinate schoolchildren based on the theory that influenza epidemics could be reduced by vaccinating schoolchildren.

• A special program of schoolchild influenza vaccination was begun in 1962, but the Japanese government abandoned the program in 1994, because of a lack of evidence that it had limited the spread of influenza in the community.

• A clear decrease in excess mortality that coincided with the timing of the schoolchild vaccination program was demonstrated after the discontinuation of the mass vaccination program.

• The program conferred a 36% adjusted mortality reduction among Japanese seniors, which corresponded to 1000 senior deaths having been averted annually.

• Discontinuation of the schoolchild influenza vaccination program was responsible for an increase in influenza-associated deaths among younger children. The total number of excess deaths of younger children (1–4 years old) from 1990 to 2000 was estimated to be 783.

• The schoolchild vaccination program was effective in reducing the number of class cancellation days and absenteeism from school.

• During the period when the mass schoolchild vaccination program was in effect, Japanese schoolchildren served as a barrier against the spread of influenza in the community.

Notes