Infant and childhood mortality in European countries prior to the 18th century was extremely high during epidemic crises. In 1722 in Britain, 74% of 1993 London burials were of children under twelve years of age, such was the risk to healthy survival posed by infectious disease. Measurement of the impact of childhood disease upon past populations is difficult. Information on past mortality is largely condensed into crude death rates: number of deaths per total population, and these have not characteristically been separated into specific age groups. Available estimates suggest that during the last six centuries in Italy, on average, cephalic mortality was 15%, and overall child mortality was 50%. During the 17th and 18th centuries in London, parental expectations of their children’s survival to early adulthood were said to be low. And in France during the late 18th century, the risk of death and/or disease from smallpox and measles was extremely high. High mortality and morbidity of these ‘milder infections’ from early exposures suggests further severity when infections were contracted in older age. But specific mortality from certain diseases in particular is hard to discern.
The pattern of childhood infections in developed societies has been described as being interrupted from the outset by death and disease. In contrast to the developing world where the pattern is often characterized as prolonged endemic disease.
2. General features of population dynamics with childhood infections.
3. Trends in exposure and infection.
4. The potential impact of HIV on childhood infection.
5. The consequences of the successful eradication of childhood infections.
6. The future of research in population infectious disease and directions for policy.
7. Conclusion.
2. Prevalence of childhood diseases
The burden of a childhood disease on society can be difficult to measure. Childhood diseases do not always have a simple and direct impact on society. They can affect short-term or long-term implications for the child or parents through impacting on the child’s ability to perform, learn, or participate in daily activities. Pain and suffering experienced by the child and parents can impact quality of life. Diseases can disrupt planned events or activities of the family and lead to financial burden through medical costs, or loss of income from taking time off work to care for a sick child. A severe disease can cause social stigmatization of the child and parents. These impacts can be hard to quantify, though can be measured through the assessment of health-related quality of life and the assigning of values to disease outcomes.
Prevalence can be measured in a variety of ways using different rates. The measurement can be the proportion of the population that has the condition at a specified time (point prevalence), the proportion of the population that has the condition during a specified time period (period prevalence), or the number of new cases of the condition during a specified time period (incidence rate). These measures can be used to look at the burden of disease in a population and show how much the disease can affect society. In addition to the death and illness caused by the disease itself, childhood diseases have many other negative effects on society. This essay will focus on the effects of diseases on the health, education, and different sectors of the economy.
3. Long-term consequences of childhood diseases
Vaccination policy for many childhood infections has been concerned solely with preventing acute mortality and morbidity, and this is still reflected in the evaluation of new vaccine candidates. An increasing recognition of the burden of long-term sequelae of childhood infections has led to efforts to prevent specific diseases that are associated with significant long-term morbidity. At the global level, the recent drive to eliminate lymphatic filariasis can be seen as a means of preventing chronic disease that is a consequence of childhood infection with the filarial parasite. In considering the cost-effectiveness of such elimination strategies, it is essential to understand the strength of association between childhood infection and chronic disease, and to appreciate the full socioeconomic impact of the chronic disease on affected communities.
Introduction
It is now recognized that many common infections of childhood can have long-term consequences on health, resulting in chronic disease and disability in adult life. The burden of long-term morbidity due to childhood diseases is difficult to measure, but has important implications for the healthcare provision in both the developed and developing world. Although vaccines have the potential to drastically reduce the incidence of many of these diseases, it is essential to understand the mechanisms by which acute infection can lead to chronic disease, in order to develop effective strategies for disease prevention.
4. Strategies for prevention and control
Simulation models have been used extensively to assess vaccination strategies, and as with the use of the vaccines themselves, these have generally been designed to prevent infection. The aim may be complete interruption of transmission as the only means of disease control or targeted at high-risk groups to reduce disease burden. Dynamic compartmental models using polio as an example have shown the potential benefits and risks of ceasing oral vaccination when disease incidence is reduced with the aim of removal of the vaccine to prevent vaccine-associated disease and spread. Older age groups were effectively protected by herd immunity, and yet there remained a high risk of importation and paralytic disease into the vaccinated country in the absence of international coordination to stop vaccination with neighboring endemic countries. High vaccine coverage in combination with surveillance has effectively controlled some vaccine-preventable diseases in countries of low socioeconomic status, as demonstrated by Bhutan’s recent control of Hepatitis B.
Eradication is the ultimate means of prevention and control and has been a major strategy to affect the public health impact of infectious diseases. It is defined as the permanent reduction to zero of the worldwide incidence of infection caused by a specific agent as a result of deliberate efforts; of which surveillance is critical to ensure long-term success. Global eradication of smallpox through vaccination stands as one of the greatest achievements of modern medicine and public health, with the last known natural case occurring in 1977. Elimination differs from eradication in that it involves halting transmission of the disease in a specific geographical area with no immediate plans to fully eradicate the causative agent globally. Whooping cough and measles were the target of elimination in the United Kingdom with good progress until concerns over vaccine safety led to decreased uptake and subsequent rise in disease incidence. Any potential net benefits of ceasing vaccination were lost, and the elimination strategy was abandoned. During this period, the diseases persisted in other parts of the world posing at times a threat of re-emergence to the UK and highlighting the importance of global coordination with the elimination strategy. Decision making regarding the global or regional nature of eradication or elimination will often require comparative assessment of disease burden and cost-effectiveness with other interventions and opportunity costs of the strategy.
Studies of the effectiveness of various strategies for the prevention and control of infectious diseases on public health are few. The methodologies used to carry out these studies are diverse and often not well described. Because of the lack of compelling evidence regarding the relative effectiveness of various strategies, most of the recommendations offered here are based on the collective wisdom of the authors and expert consultants. The CHNRI expert opinion exercise that informed a related publication that complements this series should be consulted for a research prioritization exercise when investing in interventional research. The strategies are discussed according to the epidemiological characteristics of different classes of disease.
5. Conclusion
Throughout history, the impact of childhood diseases on public health has been substantial. A century ago, infectious diseases were responsible for 30% of all deaths in the United States. Most of these diseases primarily affected children, often with devastating results. Today, the picture is much different. The implementation of childhood immunizations has greatly reduced the prevalence of a number of diseases. In particular, the world is on the brink of eradicating polio, a disease which once affected hundreds of thousands of children each year. Similarly, the use of antibiotics has almost completely eradicated certain childhood diseases such as Haemophilus Influenzae B and bacterial meningitis. The evolution of treatment and prevention for certain diseases has been particularly notable. This is best illustrated by the introduction of the Hemophilus vaccine in 1988. In the five years prior to the introduction of this vaccine, the incidence of Haemophilus Influenzae B in the United States among children under five was close to twenty thousand cases a year. In 1993, only forty-six cases were reported.