SummaryThe data from our 1968-69

During the Hong Kong influenza epidemic of 1968-1969 the attack rate among persons born prior to 1890 was about one-third the rate among persons born after 1899. During an Asian influenza epidemic in the same community two years earlier there was no apparent age effect. Most persons born before 1890 had detectable pre-epidemic antibody against A/Hong Kong/68 whereas most persons born after 1899 had no detectable pre-epidemic antibody. The lower attack rate in the older age group is consistent with the hypothesis that influenza A viruses with similar or identical hemagglutinins can reemerge over time and that remote previous experience with the same or a similar strain can be protective. Also, no age group born after 1890 was found to have a high prevalence of antibody against A/England/72 or A/Dunedin/73, the successors to A/Hong Kong/68, indicating that recycling of hemagglutinin antigens is not strictly ordered.

701observed after only three days treatment with a small dose of ethinyloestradiol it is possible that this may reflect an alteration in binding constant of thyroxine binding proteins rather than a quantitative change. The rapidity with which urinary T-4 returns to basal levels is probably due to the negative feedback control mechanism of the pituitary-thyroid axis whereby circulating levels of the free T-4 influence the release of thyrotrophin. Other possible explanations for these findings include alteration of the hepatic metabolism of T-4 after oestrogen withdrawal, which might account for, or contribute to, the increase in urinary T-4 excretion.A short course of treatment with ethinyloestradiol did not produce any significant effect on the routine serum thyroid function tests used, although pronounced changes in urinary T-4 excretion were observed. This reflects the sensitivity of the urine T-4 assay.

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