Health Inequity

The Health Inequity sub-topic explores the differences in the distribution of disease and illness within a given population. Health inequities limit people’s ability to gain access to resources and experiences required for health and well-being. Immunization is important in these populations as vaccine-preventable diseases disproportionately affect those in poorer overall health.

8 Key Concepts

Key Evidence: Among both HIV positive and HIV negative parents in a study in Kenya, 99% of pneumococcal strains found and tested were resistant to one or more antibiotics. HIV positive parents carried 16% more strains that were resistant to penicillin than those carried by HIV negative parents.

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Key Evidence: In a study of national surveillance records in South Africa, HIV positive people over 5 years of age were found to have a 43-fold risk of invasive pneumococcal disease compared to HIV negative person. This risk was highest among children age 5-19 who were found have a more than 120-fold risk of invasive pneumococcal disease compared to HIV negative uninfected children of the same age. 90% of South Africa’s invasive pneumococcal disease cases during the 5 year period occurred in the 18% of the population who are HIV positive.

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Key Evidence: Human Papillomavirus (HPV) infections are more prevalent and persistent in HIV-infected individuals -- HPV prevalence rates of 76% in HIV-infected women compared to the 46% prevalence rate in HIV-uninfected women. Cervical prevalence rates are also higher in HIV-infected women -- between 48-73% in case compared to 28% in HIV-uninfected women. Additionally, HPV infections and HPV-associated diseases appear to exert a disproportionately higher burden of disease in HIV-infected women as opposed to HIV-uninfected women.

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Key Evidence: Prior to the introduction of PCV, adults with HIV in a rural area of Kenya were nearly five times more likely to have pneumococcal pneumonia than non-infected adults, and the majority of cases with bacteremia (blood infection) occurred in HIV positive individuals.

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Key Evidence: A small hospital-based study in India found that 6 month old infants born to HIV-infected women were 11 times more likely to lack measles antibodies than 6 month olds not exposed to HIV whether or not the exposed infants were themselves infected with HIV. The lack of antibodies in most HIV-exposed infants -- making them more vulnerable to measles -- may be due to lower levels of measles antibodies in HIV-infected mothers or to poorer transfer of antibodies to the fetus across the placenta.

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Key Evidence: The Indian government childhood immunization program, UIP, designed in the 1980s to reduce the high mortality and morbidity in children, resulted in reduced infant mortality by 0.4% percentage points and under-5 mortality by 0.5%. These effects on mortality are sizable as they account for approximately one-fifth of the decline in infant and under-five child mortality rates between 1985-1990. The effects are more pronounced in rural area, for poor people, and for members of historically disadvantaged groups. The 0.5% reduction each year over 5 years (from 15% under-5 mortality in 1985 to 12.3% in 1990), represents an 18% reduction overall in under-5 mortality.

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Key Evidence: Two years after the introduction of 10-strain pneumococcal conjugate vaccine (PCV-10) in Kenya, the percent of HIV-positive adults who carried pneumococcal bacteria declined significantly (from 43% to 28%), but did not decline in HIV-negative adults. However, the reduction in carriage of pneumococcal strains that are in PCV10 declined significantly in both HIV-positive and HIV-negative adults. This reduction was still four times higher in HI- positive vs. HIV-negative adults (2.8% vs. 0.7%), indicating that HIV positive adults continue to be at considerably higher risk of invasive pneumococcal disease than HIV-uninfected adults.

From the VoICE Editors: Nasopharyngeal carriage is an indicator of the risk for invasive pneumococcal disease and pneumonia. 

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Key Evidence: Models based on demographic data from Ghana suggest that immunization would eliminate the childhood mortality risk associated with living in poverty and greatly diminish the increased risk of mortality borne by children whose parents have low levels of education.

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Key Evidence: Even though the incidence of invasive pneumococcal disease declined in all groups, including individuals on immunosuppressive drugs, following the introduction of pneumococcal conjugate vaccines for infants in Norway, people on chemotherapy were still 20 times more likely to get IPD than individuals not on any immunosuppressants, while individuals on long-term corticosteroids or other immunosuppressive drugs were around 6 times more likely to get the disease.

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Key Evidence: In survivors of pediatric and young adult cancers in the US, the risk of mortality from infectious complications is 4 times higher than in their cancer-naïve siblings. Within the first five years after cancer diagnosis, the risk of some vaccine-preventable infections such as pneumonia and hepatitis is more than 9-fold and 6-fold higher, respectively. More than 5 years after cancer diagnosis, the risk of these two infections remains high at 3.7 and 2.5 times higher than siblings.

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Key Evidence: Among children and young adults being treated for certain cancers, immunosuppressive therapies can erase immunity previously acquired through vaccination, dramatically increasing the risk of vaccine-preventable infections. The authors assert that vaccination during and after immunosuppressive treatment is necessary to rebuild immunity and protect the most at-risk children.

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Key Evidence: Within two years of the introduction of PCV10 in Mozambique, the percent of vaccinated children under five years of age with nasopharyngeal carriage of vaccine strains, declined equally in HIV-infected as in HIV-uninfected children. The vaccine-type carriage rates among both HIV-infected and uninfected vaccinated children after the vaccine was introduced were similar.

From the VoICE Editors: Pneumococcal nasopharyngeal carriage can be a precursor of invasive pneumococcal disease.

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Key Evidence: Over a five-year period following the introduction of PCV for infants in Kenya, the incidence of pneumococcal pneumonia in adults with HIV in a rural area fell sharply -- narrowing the gap in incidence rates between HIV-infected and non-infected adults -- as a result of both the herd effects of the vaccine and improved access to HIV care during this period.

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Key Evidence: A review of evidence for the use of pneumococcal conjugate vaccine in South Africa showed that children who are HIV positive are at significantly increased risk of pneumococcal disease, and so will benefit the most from vaccination, despite decreased vaccine efficacy in this group compared to healthy children.

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Key Evidence: A large randomized controlled trial of a pneumococcal conjugate vaccine in South Africa found that use of the vaccine prevented 10 times as many cases of pneumococcal pneumonia in HIV positive children than in HIV negative children.

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Key Evidence: Nearly a quarter of a million children are born with sickle cell disease in Africa each year. SCD was found to increase the risk of Hib infections by 13-fold and pneumococcal infections by 36 fold. This means that children with SCD stand to benefit enormously from PCV and Hib immunization.

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Key Evidence: In a long-term study of Canadian surveillance data researchers found that immunocompromised people were at a 12-fold risk of invasive pneumococcal disease (IPD) compared to healthy people. In addition, the risk of death from IPD in immunocompromised people was found to be 30-80% higher than healthy individuals who had contracted IPD. 10 years after introduction of PCV7 in Canada, the incidence of IPD due to serotypes included in the vaccine had decreased by 90%.

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Key Evidence: A study of children under 5 years of age in Dhaka, Bangladesh found that severely malnourished children were nearly 8 times more likely to suffer death from diarrhea than those who were not severely malnourished.

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Key Evidence: A study of Kenyan children under 5 years of age found that immunization with polio, BCG, DPT, and measles to be protective against stunting in young children (27% less likely to be stunted than unimmunized children under age 2 years). In addition, children with diarrhea and cough in the 2 weeks prior to the survey were 80-90% more likely to be underweight or to suffer from wasting.

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Key Evidence: An analysis of the association between undernutrition and mortality in young children revealed that in 60% of deaths due to diarrhea, 52% of deaths due to pneumonia, 45% of deaths due to measles and 57% of deaths attributable to malaria, undernutrition was a contributing factor.

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Key Evidence: In a US-based study of more than 65,000 longterm survivors of pediatric and young adult cancers spanning nearly three decades, researchers found an increased risk of later HPV infections and malignancies among these survivors. Female survivors of childhood and young adult cancers were found to have a 40% greater chance of developing HPV-associated malignancies compared to cancer-naïve females. This risk was even greater in male cancer survivors who had a 150% relative excess of HPV malignancies compared to cancer-naive males.

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Key Evidence: A study in the US found that the incidence of invasive pneumococcal disease was 22 to 38 times higher in adults with cancer than in healthy adults.

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Key Evidence: In a long-term study of Canadian surveillance data researchers found that immunocompromised people were at a 12-fold risk of invasive pneumococcal disease (IPD) compared to healthy people. In addition, the risk of death from IPD in immunocompromised people was found to be 30-80% higher than healthy individuals who had contracted IPD.

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Key Evidence: A study of the impact of measles vaccine in Bangladesh found that unvaccinated children in the poorest quintile were more than twice as likely to die as those from the least poor quintile. In addition, vaccination reduced socioeconomic status-related mortality differentials

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Key Evidence: An analysis of the association between undernutrition and mortality in young children revealed that in 60% of deaths due to diarrhea, 52% of deaths due to pneumonia, 45% of deaths due to measles and 57% of deaths attributable to malaria, undernutrition was a contributing factor.

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