The epidemic dynamics of three childhood infections and the impact of first vaccination in 18^thand 19^thcentury Finland

Abstract

Childhood infectious such as smallpox or measles have devasted human populations, but our knowledge on the history of public health interventions remains limited. Here, we use 100 years of newly available records in 18th and 19th century Finland to investigate the epidemic dynamics of three infections, smallpox, pertussis and measles and the impact of the first nationwide vaccination programme. Between 1750 and 1850, we found over 40 epidemics of smallpox, pertussis and measles, which together were responsible for almost 20% of all registered deaths under age 10. The start of the first vaccination programme against smallpox in 1802 promptly triggered five major changes in smallpox epidemiology: (i) decreasing mortality, (ii) increasing age at infection, (iii) increasing time between epidemics, (iv) increasing fade-outs, which all result from (v) decreased pathogen transmission. In contrast, most epidemic characteristics of the childhood infections without vaccines, pertussis and measles, changed in the opposite direction to that of smallpox: their death toll almost doubled, their reproduction number increased and pertussis, but not measles, showed a decreasing age at infection and accelerating epidemics. Our study captures a rare glimpse of the epidemiology of childhood infections in historical populations and the possible long-term impact of major public health interventions.

Grandmother presence improved grandchild survival against childhood infections but not vaccination coverage in historical Finns

“…B 290: 20230690 some of these studies did not distinguish between maternal and paternal grandmothers [19,23]. In our historical study population, childhood mortality was high and infectious diseases were the leading causes of death [32] (electronic supplementary material, table S1), which may increase the benefit of grandmother help on grandchild survival. In our study, paternal grandmother presence did not improve grandchild survival.…”

“…To identify possible ways that grandmothers benefit grandchild survival, we used extensive historical data from Finland that included causes of death, vaccination records against smallpox and family configuration to quantify the effects of grandmothers on cause-specific mortality and vaccination. Childhood infections were a leading cause of early mortality in eighteenth- and nineteenth-century Finland [31,32,55]. Maternal grandmothers improved all-cause survival of their grandchildren, which was at least in part mediated by a decrease in mortality due to smallpox, pulmonary infections and diarrhoea.…”

“…Another way that grandmothers could provide fitness benefits is by providing knowledge in childcare [25][26][27], particularly during critical times such as sickness and epidemics. In historical and in several contemporary societies, childhood infectious diseases were and are leading causes of death in children under the age of 5 years [28][29][30][31][32]. To the best of our knowledge, whether grandmother presence improves grandchild survival from childhood infections in historical societies remains unknown.…”