pneumonia and influenza (P&I) mortality rates during the 1968 pandemic among younger age groups in the United States compared to the 1980–1981 season, and the absence of any such increase among the very elderly.

These findings have significant implications for both pandemic planning and the prioritization of high-risk groups for vaccination in the scenario of vaccine shortage. Indeed, if one wishes to minimize the number of years-of-life-lost should vaccine be in short supply, then it would be more effective to immunize the middle aged and younger elderly than the very elderly.

The 1968 pandemic experience in Europe was different from that of the United States. It began with the rapid spread of a new virus, which reached Europe about 2 months after its emergence in Hong Kong (Cockburn et al., 1969). But influenza activity remained curiously weak in the wave that occurred during the 1968–1969 winter in Europe (Assaad et al., 1973; Stuart-Harris, 1970). At the same time, influenza-related mortality and morbidity increased substantially in the United States, especially among the young (Housworth and Spoon, 1971). More surprising, a much more severe wave occurred in the United Kingdom during the winter of 1969–1970, although no change in the circulating strain had been identified (Miller et al., 1971). We revisited the pandemic experience in the United States and the United Kingdom by extending the analysis of mortality data from both countries (Figure 1-8) to better describe and possibly explain the geographical differences.

FIGURE 1-8 Monthly pneumonia and influenza (P&I) mortality rate during the first two waves of the 1968 pandemic (A/H3N2) in the United Kingdom. Epidemic threshold determined by a spline-Serfling regression model.