VoICE : Search Immunization Evidence

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The VoICE tool is a compendium of the many direct and downstream impacts of vaccine-preventable disease and immunization. The database contains summary explanations of the link between immunization and each impact, as well as sources of evidence for each link. You can browse the VoICE tool by topic, or use the filters to find results based on topic, disease or vaccine, location and published year.

24 Key Concepts, 26 Sources
Key Concept

Key Evidence: A study modeling the relationship between disease and poverty in Ethiopia found that among the top 20 causes of death in Ethiopia, diarrhea and lower respiratory infections (LRIs) are the top two drivers of medical impoverishment. It is estimated that in 2013, out-of-pocket direct medical costs for diarrheal disease drove an estimated 164,000 households below the poverty line (representing 47% of all the diarrhea cases), and LRIs led to an estimated 59,000 cases of poverty (17% of LRI cases). Of the top 10 health-associated drivers of poverty, four are at least partially vaccine-preventable (1. Diarrhea, 2. LRI, 4. TB. 10. Pertussis).

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Key Concept

Key Evidence: In a study of a 2003 outbreak of pertussis in the U.S., including 17 cases among healthcare workers, researchers estimated that vaccinating healthcare workers would prevent nearly 50% of disease exposures by healthcare workers per year.

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Key Concept

Key Evidence: In Tanzania, poverty was found to have a negative effect on receiving vaccines on time (at the recommended age). Children in the wealthiest quintile experienced 19% fewer delays for BCG vaccination, 23% fewer delays for the third dose of DTP vaccination, and 31% fewer delays for the first dose of measles-containing vaccine compared to children of the poorest quintile.

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Key Concept

Key Evidence: Children in Tanzania living 5 km or greater distance from the nearest healthcare facility were less likely to be immunized than children living less than 5 km from facilities. Compared to children living close a health facility, children far from a health facility had almost three times the risk of missing out on BCG, 84% higher risk of missing the third dose of DTP, and 48% higher risk of missing the first dose of measles-containing vaccine. Of children who did receive BCG, those living more than 5 km from facilities were 26% more likely to received BCG vaccine late than children close to the facility.

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Key Concept

Key Evidence: A small study from the Philippines, published in a Working Paper from Harvard University, found that children immunized with 6 basic vaccines scored better on three cognitive tests (verbal, mathematics and language) at age 11 compared to children who received none of these 6 vaccines.

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Key Concept

Key Evidence: Considering both the direct and indirect costs, researchers in the Netherlands estimated that the preventative immunization of Dutch healthcare workers (HCW) against pertussis (to reduce exposure and transmission contributing to outbreaks) results in a return on investment of 4 Euros to every 1 euro invested. This projection assumes an outbreak of pertussis once every 10 years.

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Key Evidence: In a study of a 2003 outbreak of pertussis in the U.S., including 17 cases among healthcare workers, researchers estimated that vaccinating healthcare workers would result in a 2.4-fold return on investment for hospitals.

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Key Concept

Key Evidence: Children who were born as the fourth or fifth child in their household were more than twice as likely to be incompletely vaccinated with BCG, measles vaccine, and pentavalent vaccine than those who were born as the second or third child in their household.

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Key Concept

Key Evidence: In Japan, which has experienced a re-emergence of pertussis among adolescents and adults, vaccinating pregnant women with the Tdap vaccine would be cost effective in preventing the illness in young infants (<3 months of age) and in mothers, according to the WHO definition of cost effectiveness. This is true even if only 50% of pregnant women receive the vaccine.

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Key Evidence: Pertussis causes nearly 200,000 deaths in children worldwide, nearly all in infants too young to be vaccinated. Vaccinating pregnant women against pertussis with a single dose of Tdap vaccine would be 89% effective in protecting infants against the disease over their first 2 months of life and would reduce pertussis incidence in newborns in the U.S. by 68% (assuming 75% of mothers are vaccinated). This strategy is cost-effective, whereas vaccinating the father before the birth or vaccinating parents and/or other family members after the child is born would not be.

From the VoICE Editors: The analysis assumes a vaccination cost of ≈$44 per dose.

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Key Concept

Key Evidence: A study in Australia estimated that adding dTpa vaccination for pregnant women to the current pertussis immunization program for children would prevent an additional 8,800 symptomatic pertussis cases (mostly unreported) and 146 hospitalizations each year in all ages, including infants and their mothers, as well as one death every 22 months. The study found maternal pertussis vaccination to be cost-effective.

From the VoICE Editors: Note: The formulation used in this study is abbreviated dTpa.

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Key Concept

Key Evidence: In a study of immunization in the Philippines, children vaccinated against 6 diseases performed significantly better on verbal reasoning, math, and language tests than those who were unvaccinated. (note: Researchers did not find an association with physical growth.)

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Key Concept

Key Evidence: Wealth and mother’s education are significant predictors of vaccination rates in both urban and rural settings. However, low paternal education, lack of antenatal care, and home births were significantly associated with low vaccination rates only in rural settings. This suggests the need for tailored vaccine programs.

From the VoICE Editors: This study compared the significance of risk factors for low vaccination rates in rural versus urban settings in Tanzania.

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Key Evidence: A study conducted in Eastern Uganda found that Ugandan children whose mothers had some secondary schooling were 50% more likely to have received scheduled vaccinations by 6 months of age than children whose mothers had attended school only through primary level. This effect became more pronounced with delivery of the later doses of each vaccine (OPV2, 3 & DPT-HB-Hib 2,3).

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Key Concept

Key Evidence: A study looking at WHO data from member states shows that globally, coverage of the third dose of DTP is 26% higher among children born to mothers with some secondary education compared to mothers with no education.

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Key Evidence: Researchers looking at vaccination coverage in 45 low- and middle-income countries found that maternal education is a strong predictor of vaccine coverage. Children of the least educated mothers are 55% less likely to have received measles containing vaccine and three doses of DTP vaccine than children of the most educated mothers.

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Key Concept

Key Evidence: An impact evaluation for a women’s empowerment program in India found that the children of mothers who participated the empowerment program were significantly more likely to be vaccinated against DTP, measles, and tuberculosis than children of mothers not involved in the program. This study also found that the women’s empowerment program had positive spillover effects: In villages where the program occurred, children of mothers not in the program (non-participants) were 9 to 32% more likely to be immunized against measles than in villages where the program did not occur (controls). Overall, measles vaccine coverage was nearly 25% higher in the program villages compared to the control villages.

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Key Concept

Key Evidence: In an analysis of immunization coverage in 45 low- and lower-middle income Gavi-eligible countries, researchers found that overall, maternal and paternal education were two of the most significant drivers of coverage inequities in these countries. Pooling the data from all countries, the authors found that “children of the most educated mothers are 1.45 times more likely to have received DTP3 than children of the least educated mothers.” The same held true for measles vaccines with a 1.45-fold likelihood of vaccination in children of the most educated mothers.

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Key Concept

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 Concept

Key Evidence: Globally, coverage of the third dose of DTP is 15% higher among children in the highest compared to lowest wealth quintile. However, this masks differences of up to 64% in the most inequitable countries (Nigeria).

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Key Evidence: In Tanzania, poverty was found to have a negative effect on receiving vaccines on time (at the recommended age). Children in the wealthiest quintile experienced 19% fewer delays for BCG vaccination, 23% fewer delays for the third dose of DTP vaccination, and 31% fewer delays for the first dose of measles-containing vaccine compared to children of the poorest quintile.

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Key Concept

Key Evidence: A study in Kenya revealed that immunization with polio, BCG, DPT and measles had protective effects with respect to stunting in children under 5 years of age. In children under the age of 2 years, immunized children were 27% less likely to experience stunting when compared to unimmunized children. Additionally, children who suffered from cough or diarrhea in the 2 weeks prior to the study showed an 80-90% higher probability of being underweight or experiencing wasting.

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Key Concept

Key Evidence: A study of Kenyan children under 5 years of age found that 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 Concept

Key Evidence: Pregnant women are at particularly high risk of serious illness and death from a variety of bacterial and viral diseases, such as influenza, pneumococcal pneumonia, and Group B strep, for which vaccines exist or are in development. Vaccine-preventable diseases in pregnancy are associated with adverse pregnancy outcomes such as spontaneous abortion, congenital anomalies, preterm birth, and low birth weight.

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Key Concept

Key Evidence: In Brazil, where pertussis cases have climbed, mainly in infants <4 months of age, vaccinating pregnant women with Tdap vaccine at the same coverage rate as influenza vaccination in pregnant women (57%) would reduce pertussis cases in children under 1 year of age by 41%, deaths by 43%, and would be cost-effective, according to the WHO thresholds.

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Key Evidence: In Japan, which has experienced a re-emergence of pertussis among adolescents and adults, vaccinating pregnant women with the Tdap vaccine would be cost effective in preventing the illness in young infants (<3 months of age) and in mothers, according to the WHO definition of cost effectiveness. This is true even if only 50% of pregnant women receive the vaccine.

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Key Evidence: Pertussis causes nearly 200,000 deaths in children worldwide, nearly all in infants too young to be vaccinated. Vaccinating pregnant women against pertussis with a single dose of Tdap vaccine would be 89% effective in protecting infants against the disease over their first 2 months of life and would reduce pertussis incidence in newborns in the U.S. by 68% (assuming 75% of mothers are vaccinated).

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Key Evidence: A study in Australia estimated that adding dTpa vaccination for pregnant women to the current pertussis immunization program for children would prevent an additional 8,800 symptomatic pertussis cases (mostly unreported) and 146 hospitalizations each year in all ages, including infants and their mothers, as well as one death every 22 months. The study found maternal pertussis vaccination to be cost-effective.

From the VoICE Editors: Note: The formulation used in this study is abbreviated dTpa.

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Key Evidence: A large study in California involving nearly 150,000 newborns found that vaccinating pregnant women with the Tdap vaccine provided 91% protection against pertussis infection among infants under 2 months of age and 88% protection before the infants had any vaccinations. The study also showed that vaccinating mothers during their pregnancy did not reduce the effectiveness of infant vaccination but that maternal Tdap vaccination provided additional protection to the infants through their first year of life.

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Key Evidence: In Argentina, more than 50% of deaths due to pertussis occurred in infants younger than 2 months of age — too young to be vaccinated in the country. The impact of maternal pertussis vaccination in protecting their infants against the disease reduced the incidence of pertussis in infants less than 2 months old by half, when comparing states with high and low maternal vaccination rates.

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Key Evidence: Vaccinating women during their second or third trimester of pregnancy with the Tdap vaccine was 81% effective in preventing pertussis in their infants in the first two months of life, according to a case-control study in Argentina.

From the VoICE Editors: This is one of the first studies to measure the effectiveness of maternal pertussis vaccination in a middle-income country and its findings support Argentina’s decision to introduce the vaccine.

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Key Evidence: The period following delivery but before an infant acquires immunity to diseases by natural exposure or immunization — is when infant mortality from infections is highest. Vaccinating pregnant women has shown to be effective in protecting young infants against influenza and pertussis.

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Key Evidence: Immunization against tetanus, pertussis and influenza during pregnancy has been shown to have a profound effect on the health of the mother and fetus, and increases survival of infants in their first months of life. Maternal immunizations with tetanus toxoid-containing vaccines has been one of the main contributors to the 94% reduction in global deaths due to tetanus since 1988. Between the 1970s to the early 2000s, maternal immunization against pertussis brought disease incidence down to 5,000 cases per year from the earlier 100,000-250,000 cases per year in the United States. Vaccination of mothers for influenza has brought down confirmed cases of the disease by 63%.

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Key Evidence: Vaccinating pregnant women against pertussis at least one week before delivery was found to be 91% effective in preventing the disease in infants <3 months old and 95% effective in preventing infant deaths in a study conducted in England over a 3-year period following the introduction of dTap-IPV vaccine for pregnant women. Of the 37 deaths from pertussis in infants that occurred in England from 2009 to 2015, 32 (86%) were in infants <2 months of age, highlighting the vulnerability of very young infants to severe pertussis. All but 2 of the deaths in <2 month olds were in children whose mothers hadn’t been vaccinated against pertussis during their pregnancy, while in the 2 other cases, the vaccination occurred too late in the pregnancy (<10 days before the birth).

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Key Evidence: In a case-control study in the state of São Paulo, Brazil, vaccination of pregnant women with Tdap vaccine was 83% effective in preventing pertussis in their infants less than 2 months of age — before their first dose of DPT — and 81% effective after controlling for household income and mother’s age.

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Key Evidence: Infants less than 2 months old are too young to be vaccinated against pertussis yet are at highest risk of severe disease – – a 75% hospitalization rate and a 1% case fatality rate. A case-control study in six U.S. states found that vaccinating women during the third trimester of pregnancy with Tdap vaccine provided 81% protection against pertussis to infants <2 months and 91% protection against hospitalized cases of pertussis.

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Key Concept

Key Evidence: A recent review looks at evidence linking vaccinations in early infancy to childhood development services. BCG and DPT have the highest coverage of any vaccines worldwide and are typically administered within 6 weeks of birth. This timing offers the opportunity to deliver a range of early childhood development interventions such as newborn hearing screening, sickle cell screening, treatment and surveillance, maternal education around key newborn care issues such as jaundice, and tracking early signs of poor growth and nutrition.

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Key Concept

Key Evidence: Increased uptake of immunization for vaccine-preventable diseases, particularly in low- and middle-income countries, could save the lives of thousands of mothers and children each year. The disease burden of tetanus, influenza, and pertussis has been minimized in many countries through maternal immunization, but wider applications of this strategy are now needed.

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Key Concept

Key Evidence: A study in Australia estimated that adding dTpa vaccination for pregnant women to the current pertussis immunization program for children would prevent an additional 8,800 symptomatic pertussis cases (mostly unreported) and 146 hospitalizations each year in all ages, including infants and their mothers, as well as one death every 22 months. The study found maternal pertussis vaccination to be cost-effective.

From the VoICE Editors: Note: The formulation used in this study is abbreviated dTpa.

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Key Concept

Key Evidence: Wealth and mother’s education are significant predictors of vaccination rates in both urban and rural settings.  However, low paternal education, lack of antenatal care, and home births were significantly associated with low vaccination rates only in rural settings. This suggests the need for tailored vaccine programs.

From the VoICE editors: This study compared the significance of risk factors for low vaccination rates in rural versus urban settings in Tanzania. 

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Key Evidence: Globally, coverage of the third dose of DTP is 8% higher among urban dwellers compared to children raised in a rural environment.

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