Background: An important consequence of influenza epidemics is increased mortality in elderly persons and those with high-risk conditions. Most developed countries have focused on vaccination of this group. In Japan, the control of influenza centered on the vaccination of schoolchildren. From 1962 to 1987, most Japanese schoolchildren received influenza vaccine. With the level of coverage achieved, it is possible that herd immunity was achieved. If this were the case, the impact of disease should have been reduced in older persons, and a reduction in winter excess mortality should have occurred. Methods: All-cause and pneumonia and influenza (P&I) excess mortality for both Japan and the US were estimated for 50 winters, 1949–1998. Results: Estimates of P&I and all-cause excess mortality were highly correlated. The winter excess of mortality in Japan was sharply reduced from ~1963 to about 1990, after which it again rose. The timing of these changes matches that of the Japanese Schoolchildren Vaccination Program. Conclusions: All-cause and P&I mortality represent the impact of influenza about equally well. That impact is three to four times greater in Japan than in the US. Schoolchildren vaccination appears to have averted ~37,000 deaths/year, or one for each ~420 vaccinations; and must be included in comprehensive pandemic planning.