Immune responses to measles and smallpox vaccinations in malnourished children

Factors That Influence the Immune Response to Vaccination

There is substantial variation between individuals in the immune response to vaccination. In this review, we provide an overview of the plethora of studies that have investigated factors that influence humoral and cellular vaccine responses in humans. These include intrinsic host factors (such as age, sex, genetics, and comorbidities), perinatal factors (such as gestational age, birth weight, feeding method, and maternal factors), and extrinsic factors (such as preexisting immunity, microbiota, infections, and antibiotics). Further, environmental factors (such as geographic location, season, family size, and toxins), behavioral factors (such as smoking, alcohol consumption, exercise, and sleep), and nutritional factors (such as body mass index, micronutrients, and enteropathy) also influence how individuals respond to vaccines. Moreover, vaccine factors (such as vaccine type, product, adjuvant, and dose) and administration factors (schedule, site, route, time of vaccination, and coadministered vaccines and other drugs) are also important. An understanding of all these factors and their impacts in the design of vaccine studies and decisions on vaccination schedules offers ways to improve vaccine immunogenicity and efficacy.

Nutrition and Infectious Diseases in Developing Countries and Problems of Acquired Immunodeficiency Syndrome

Infectious diseases are the major causes of death and morbidity in underdeveloped countries, particularly in children. Increasing evidence suggests that malnutrition—both Protein-Energy type Malnutrition (PEM) and essential micronutrient (vitamins, trace minerals, essential amino acids, polyunsaturated fatty acids) type—is the underlying reason for increased susceptibility to infections. On the other hand, certain infectious diseases also cause malnutrition, which results in a vicious cycle. Before its viral origin was known, acquired immunodeficiency syndrome (AIDS) had been termed the thin disease because cachexia was AIDS' main clinical manifestation.

The relationship between infection and malnutrition is well documented in the literature. Our experience supports this. Preventive and therapeutic measures are suggested.

Malnutrition and vaccination in developing countries

Malnutrition contributes to an estimated 45% of deaths among children under 5 years of age in developing countries, predominantly due to infections. Malnourished children therefore stand to benefit hugely from vaccination, but malnutrition has been described as the most common immunodeficiency globally, suggesting that they may not be able to respond effectively to vaccines. The immunology of malnutrition remains poorly characterized, but is associated with impairments in mucosal barrier integrity, and innate and adaptive immune dysfunction. Despite this, the majority of malnourished children can mount a protective immune response following vaccination, although the timing, quality and duration of responses may be impaired. This paper reviews the evidence for vaccine immunogenicity in malnourished children, discusses the importance of vaccination in prevention of malnutrition and highlights evidence gaps in our current knowledge.

Advances in Monitoring Have Not Translated into Improvements in Humanitarian Health Services

Background:

This paper is an attempt to review the advances and shortfalls in data collection and use of health data that have occurred during health emergencies in recent decades for the opening session of the Humanitarian and Health Conference at Dartmouth University in September of 2006.

Methods:

Examples of various kinds of successes and failures associated with health data collection are given to highlight advances with an effort to emphasize multi-agency efforts reviewed by outside scholars.

Results:

Health data, particularly surveillance data, have allowed relief workers to set priorities for life-saving humanitarian programs. The main guidelines widely utilized such as those of the US Centers for Disease Control and Prevention, Médecins sans Frontières, and the Sphere Project have considerable similarity due to the consistency of data collected in various crises. Moreover, difficult to see problems and successes have been revealed by coherent surveillance efforts. Yet, these data collection efforts can not show significant improvements in the quality of humanitarian aid in recent years. Moreover, health data often do not appear to have meaningful influence on the prioritizing of relief resources globally or on those political issues that trigger emergencies.

Conclusions:

The field of humanitarian relief is relatively nascent. Methods for documenting basic health measures on the local level have been developed and general health priorities have been documented. Some technical improvements in monitoring still are needed but decision-making is most often limited by the lack of data rather than the problems with data. The ability of health data to influence spending global priorities, legal or political actions undertaken by international organizations, remains very limited.

Landscape analysis of interactions between nutrition and vaccine responses in children

The world's poorest children are likely to be malnourished when receiving their childhood vaccines. It is uncertain whether this affects vaccine efficacy and whether the coadministration of nutrient supplements with vaccines has beneficial or detrimental effects. More recently, a detrimental interaction between vitamin A (VA) supplementation (VAS) and the killed diphtheria-tetanus-pertussis vaccine given in early childhood has been suggested. This report provides a critical review of the published interactions between nutritional status and/or supplementation and vaccine responses in children. Due to an absence of evidence for most nutrients, this analysis focused on protein-energy, vitamins A and D, and iron and zinc. All vaccines were considered. Both observational studies and clinical trials that led to peer-reviewed publications in English or French were included. These criteria led to a pool of 58 studies for protein-energy malnutrition, 43 for VA, 4 for vitamin D, 10 for iron, and 22 for zinc. Our analysis indicates that malnutrition has surprisingly little or no effect on vaccine responses. Evidence for definitive adjunctive effects of micronutrient supplementation at the time of vaccination is also weak. Overall, the paucity, poor quality, and heterogeneity of data make it difficult to draw firm conclusions. The use of simple endpoints that may not correlate strongly with disease protection adds uncertainty. A detailed examination of the immunological mechanisms involved in potential interactions, employing modern methodologies, is therefore required. This would also help us understand the proposed, but still unproven, negative interactions between VAS and vaccine safety, a resolution of which is urgently required.

Seroprevalence of anti-polio antibodies in a population 7 months to 39 years of age in Uruguay: Implications for future polio vaccination strategies

This study evaluated the seroprevalence of poliovirus types 1, 2 and 3 antibodies and vaccination coverage in 780 subjects aged between 7 months and 39 years in Montevideo, Uruguay, where oral polio vaccine (OPV) is used. Antibody titers were measured and seroprotection rates and geometric mean titers (GMTs) were compared among four age groups. Vaccination histories were recorded from documents and interviews. Seroprotection rates ranged from 72% to 95% in children aged 7-23 months, 31-77% in 2-9-year olds, 14-45% in 10-19-year olds and 20-59.5% in 20-39-year olds. Seroprotection decreased significantly with increasing age (p<0.05). Polio vaccination coverage was >90% for the two youngest age groups. These results could help guide public policy decisions regarding polio vaccination, and support the use of inactivated polio vaccine following cessation of OPV.

Follow-up of the antibody response to measles vaccine in a rural area of Guinea-Bissau

One hundred and fourty-four children who either were already immune or had been successfully immunized against measles were reexamined after 16 months. All still had circulating Elisa antibodies at a clearly detectable level. Titres were higher in the group of children stated to have had measles prior to the immunization. None of the children had measles after immunization. Boostering by the wild virus may have occurred, whereas no evidence of a booster effect from the vaccine was found. About one third of the children were underweight. Plasmodium falciparum parasitaemia rate, and also its seasonality, varied with the location of the child's homestead. Even children exposed to mesoendemic P. falciparum malaria and moderate malnutrition can be successfully immunized with a conventional live attenuated measles vaccine from 8 months of age, which probably results in a lasting protection.

Current concepts in immune derangement due to undernutrition

Protein-calorie malnutrition (PCM) adversely affects more or less all immune competent cells. Nonspecific immunity is impaired, particularly adherence and chemotaxis of phagocytes, although the responsiveness of circulating cells may not be the same as that of noncirculating cells. PCM results in numerical and functional impairment in lymphocytes. PCM markedly affects IgG class antibodies which have the highest affinity when directed against T-dependent antigens. These impairments are interrelated, since cooperation between T-helper cell and B-cells is depressed, and the antigen presentation to T-helper cells by macrophages is deficient.

Response to measles vaccine in Haitian infants 6 to 12 months old. Influence of maternal antibodies, malnutrition, and concurrent illnesses

To study the factors affecting the serologic response to measles vaccination, we evaluated 595 Haitian infants from 6 through 12 months of age, and their mothers, at the beginning of an immunization program. Thirty-four per cent of the infants had preexisting serologic evidence of measles infections by 11 months of age. Among infants more than nine months of age, those who had had measles had a significantly lower nutritional status than those who had not (P less than 0.01). After vaccination, seroconversion rates increased from 45 per cent at 6 months to 100 per cent at 12 months. The lowest rate of vaccine failure compatible with acceptably low rates of natural infections could be achieved by vaccination after eight months of age. Infants born to mothers with low levels of antibody to measles (hemagglutination-inhibition antibody titers less than 1:40) were significantly more likely to have had natural measles (P less than 0.01) or to have seroconversion after vaccination (P less than 0.001) at 6 to 10 months of age than were infants born to mothers with higher of age than were infants born to mothers with higher titers. Malnutrition and acute infections did not affect seroconversion rates. These data support the World Health Organization recommendation to administer measles vaccine in under-developed countries as soon after nine months of age as possible, regardless of nutritional status or the presence of minor illnesses.

Introduction of measles into a highly immunised West African community: the role of health care institutions

In an urban area of Guinea-Bissau, where more than 80% of the children have been vaccinated, measles continues to be a major cause of child mortality. Compared with the period before the introduction of vaccination, more cases occur outside the community, while more cases within the district are now guests and newcomers. Half of the new introductions of measles into the community and 30% of the measles deaths can be traced back to the paediatric ward. Contact with health care institutions plays an important role in the transmission of measles, particularly among the youngest children. This consequence of health care may be avoidable, however, since several studies suggest that sick children can be vaccinated safely and effectively.

[Measles: optimum age and number of doses recommended for vaccination in Brazil]

Este estudo foi inicialmente conduzido em população adulta normal, compreendendo doadores de Banco de Sangue, estudantes universitários e parturientes, totalizando 889 indivíduos. Foi observado que cerca de 87% desta população apresentava anticorpos específicos para o sarampo, e que o mesmo porcentual de positividade observado nas gestantes, foi encontrado nos seus respectivos conceptos dada a passagem transplacentária dos anticorpos maternos. Foi verificado o declínio desses anticorpos após o 4.° mês, do recém-nato. Os resultados à vacinação contra o sarampo foi estudada em 1268 crianças divididas em três grupos: I) vacinadas aos 7 meses e revacinadas aos 15 meses; II) vacinadas aos 9 meses e III) vacinadas aos 7 meses e revacinadas aos 9 meses. Os resultados deste estudo indicam que apesar da resposta à vacinação ter sido mais eficiente no grupo de crianças maiores, é importante que se vacine aos 7 meses de idade, embora a porcentagem de soroconversão tenha sido de 50%. Esta medida deve ser levada em consideração, tendo em vista que a mortalidade por sarampo em crianças com menos de 1 ano representa a metade dos óbitos pela doença. Foi verificado que após a aplicação da 2.° dose, não houve diferença quanto à soroconversão, tanto no grupo revacinado 2 meses ou 8 meses após a 1.º dose da vacina. Portanto, a vacinação aos 7 meses é necessária, visando diminuir a mortalidade e a morbidade dentro do 1.º ano de vida, e a revacinação aos 9 meses, a fim de imunizar as crianças não beneficiadas com a 1.ª dose.

Immune function in the malnourished host

Deficiencies of protein, energy, and specific vitamins and minerals impair function of various components of the immunological network and therefore weaken host defense. These various deficiencies may affect specific loci within the network, but because of the interrelations between the different systems, the ultimate effect may be quite broad. Patients with PEM often suffer infections, which may also impair the immune function. It is difficult to separate effects of malnutrition from those of infection, a fact recognized in the recent coinage of the term malnutrition-infection complex. On the basis of the available information it appears that PEM and associated deficiencies of nutrients cause a major impairment in the T lymphocytes and the complement system. They have relatively less effect on the B lymphocytes and the phagocytes directly; however, normal B cell activity is dependent on regulatory influences of T cells and the phagocytic cells require mediators generated from the activation of complement. Therefore these cells also are functionally defective in PEM. The consequence of these deficiencies of function of the immune system in the malnourished host is heightened susceptibility to and a less vigorous response to infections. These defects can be generally reversed by nutritional rehabilitation.

T and B lymphocyte function in response to a protein-free diet

Groups of female adult rats were fed either isocaloric protein-free or 18% protein diets for various intervals. Four days before sacrifice, the animals were immunized either with sheep erythrocytes or with a trinitrophenyl-lipopolysaccharide (TNP-LPS) conjugate. Spleen lymphoid cell populations, spleen plaque-forming cells, and serum hemolysins were measured. A persistent diminution, proportional to the duration of protein deprivation, was observed in all parameters studied after immunization with the T-dependent antigen, sheep erythrocytes. The immune dysfunction was more pronounced for hemolysin titers, which became undetectable after 15 days of protein-free diet. The response of the protein-free group to the T-independent antigen (TNP-LPS) after 15 days of diet was only 34% of the control. When a T-cell lymphokine, macrophage migration inhibitory factor, was measured, a normal response was observed in the protein-free group. Feeding a normal diet rapidly restored the spleen plaque-forming cell populations to 60% of normal after 4 days and to 100% after 6 days. Protein starvation influenced the production of antibodies more than it did the number of antibody-forming cells. The nutritional impairment of immunoglobulin synthesis appears to be reversible.

Measles in the tropics and public health practice

Measles shows three distinct transmission patterns in the tropics, one each in urban, rural and insular or very remote areas. The characteristics of measles transmission are reviewed for each area, both with and without immunization. Planning must be based on the best use of currently underused infrastructure in the light of epidemiology. Mass mobile campaigns are not advised for urban areas. Vaccination of the sick and the well as part of episodic medical care is proposed, and vaccination of the sick is supported as safe and effective. Age floors and ceilings should be set with reference to the local situation; adoption of international "rules of thumb", without reference to local conditions, is inadvisable." A mixed strategy is urged for rural areas, with routine immunization against measles as part of a multi-antigen programme. Routine immunization should be complemented by annual surveillance and containment during the seasonal trough. Research and development needs in measles control include better understanding of measles epidemiology, more operationally useful quantitative models, and trials of new control strategies. Control, elimination and eradication are defined and discussed.

Host defense mechanisms in protein energy malnutrition

This review has focused on effects of protein energy malnutrition on immune responses in the human host. These studies document major impairment of the T-cell and complement systems in severe PEM, and less profound, but probably significant, effects upon B-cells and immunoglobulins, particularly SIgA. While mild-moderate malnutrition also alters the T-cell system and may predispose to infection, there is less evidence to suggest that complement is similarly affected. Indeed, some data suggest that the host with mild to moderate malnutrition is still able to respond to stress with an acute phase serum protein response and to boost serum levels of complement and complement activity. This may be a functionally significant distinction, serving to separate the more from the less severely ill. Because many other factors alter immune responses, including vitamins, calories, and trace metals, and few clinical studies have examined these parameters, it is uncertain how much of the problem in malnutrition is due to protein, to energy intake, to iron, to other micronutrients and trace minerals, to vitamin E or to other vitamins alone or in combination with deficiencies in protein and energy. Other chapters in this volume attempt to sort out these questions in animal studies, but the relevance of these data for the human situation will remain uncertain until the investigations are carried out in humans as well.

Rapid assessment of health status and preventive-medicine needs of newly arrived Kampuchean refugees, Sa Kaeo, Thailand

In the disaster relief programme for Kampuchean refugees in Thailand, epidemiological techniques were incorporated into the health-planning process during the first 2 weeks of the refugee influx. The findings influenced not only health care in the first refugee camp but also the delivery of medical services in subsequent camps. The mortality rate in the first week of refugee settlement was 9.1/10 000/day, and fell to 0.71/10 000/day by the fifth week. Children aged 4 and under had the highest risk of death. Fever/malaria was the main cause of morbidity and mortality. Simple epidemiological techniques, if initiated early in the relief effort, can influence medical decisions and lead to more effective use of health resources.