The Knowledge Hub

What is the Knowledge Hub?

Explore the VoICE Knowledge Hub—a searchable database featuring the latest peer-reviewed research on immunization benefits, especially in low- and middle-income countries. Browse the Knowledge Hub using a variety of different filters to find vaccine evidence based on country, region, topic, or disease. Click on a tag to find more evidence on a specific area, such as the return on investment of vaccines or impacts of infectious disease outbreaks.


Diseases & Vaccines


WHO Regions


Immunization Terms

The introduction of the dTpa vaccine for pregnant women in Brazil reduced pertussis hospitalizations in infants

In response to an increase in pertussis cases beginning in 2010, Brazil introduced dTpa vaccine into the national immunization schedule for pregnant women in 2013. In the pre-maternal vaccination period (2011–2013), the average annual incidence of pertussis hospitalizations in children under 1 year old was 98.3/100,000 and in the post-maternal vaccination period (2015–2017) the average was 65.9/100,000, a decline of 32.9%.

Friedrich F, Valadão MC, Brum M et al.. 2020. Impact of maternal dTpa vaccination on the incidence of pertussis in young infants. PLoS ONE. 15(1).

Immunization campaigns provide more equitable access to childhood vaccinations compared to maternal health services

An analysis of survey data in Latin America and Caribbean countries found that DPT3 coverage rates among indigenous children were significantly lower than in children of European or mixed ethnicity in three out of 14 countries, while significant inequities between these groups in coverage of maternal health services, such as antenatal care and delivery by a skilled birth attendant, existed in most of the countries. The greater equity in access to childhood vaccination by ethnic group may be because vaccinations are often delivered in the communities through immunization campaigns, whereas maternal health services require accessing health facilities, which may incur user fees and transportation costs.

Mesenburg MA, Restrepo-Mendez MC, Amigo H et al.. 2018. Ethnic group inequalities in coverage with reproductive, maternal and child health interventions: cross-sectional analyses of national surveys in 16 Latin America and Caribbean countries. Lancet Global Health. 6(8).

Vaccinating pregnant women with Tdap vaccine in Brazil was 83% effective in preventing pertussis in infants

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.

Fernandes EG, Sato APS, Vaz-de-Lima LRA et al.. 2019. The effectiveness of maternal pertussis vaccination in protecting newborn infants in Brazil: a case-control study. Vaccine. 37(36).

Vaccinating pregnant women in Brazil with Tdap vaccine would greatly reduce pertussis cases and deaths in infants

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.

Sartori AMC, de Soarez PC, Fernandes EG et al.. 2016. Cost-effectiveness analysis of universal maternal immunization with Tdap vaccine in Brazil. Vaccine. 34(13).

Vaccination of infants against pneumonia greatly reduces hospitalizations, saving millions in healthcare costs

In a study using actual data on hospitalizations and costs before and after PCV-10 vaccine was introduced in Brazil, an estimated 463,000 hospitalizations from all causes of pneumonia were prevented in persons less than 65 years of age over 5 years following introduction of the vaccine — saving an estimated US$147 million in hospitalization costs. Half of the costs averted were due to fewer hospitalizations in children under five, who were targeted for the vaccine, while the remaining half were due to fewer hospitalizations in persons 5-49 years of age, as a result of herd protection.

Andrade AL, Afonso ET, Minamisava R et al.. 2017. Direct and indirect impact of 10-valent pneumococcal conjugate vaccine introduction on pneumonia hospitalizations and economic burden in all age groups in Brazil: A time-series analysis. PLoS One. 12(9).

Immunization can prevent costly meningitis outbreaks

Two meningococcal meningitis outbreaks in Brazil resulted in US$128,000 (9 cases, 2007) and US$34,000 (3 cases, 2011) in direct costs to the health system to investigate cases and manage the outbreak (including emergency vaccination). The investigation and response activities related to the 2011 outbreak alone cost $11,475 per case, and an additional $6,600 overall for supplemental disease surveillance activities.

Constenla D., Carvalho A., Guzman NA.. 2015. Economic impact of meningococcal outbreaks in Brazil and Colombia. Open Forum Infectious Diseases. 2(4).

Immunization can help reduce the risk of stunting caused by diarrhea in children

A pooled analysis of nine studies assessing the effects of diarrhea on stunting prior to the age of 24 months showed that the odds of stunting were significantly increased with each diarrheal episode. Each day of diarrhea prior to attaining 24 months of age also contributed to the risk of stunting. For each five episodes of diarrhea, the odds of stunting increased by 13%. In addition, once a child becomes stunted, only 6% of those stunted at 6 months of age recovered by 24 months of age.

Checkley, W., Buckley, G., Gilman, R.H., et al.. 2008. Multi-country analysis of the effects of diarrhoea on childhood stunting. International Journal of Epidemiology. 37(4).

Immunization with rotavirus vaccine may also reduce severe gastroenteritis cases in unimmunized children through herd immunity

A meta-analysis of studies measuring the impact of rotavirus vaccine (RVV) on severe gastroenteritis morbidity and mortality, found a 22% herd immunity effect for severe rotavirus gastroenteritis in children less than one year of age in US and El Salvador.  In Latin America, severe gastroenteritis due to any cause was reduced by 25%.

Pollard, S.L., Malpica-Llanos, T., Friberg, I.K., et al.. 2015. Estimating the herd immunity effect of rotavirus vaccine. Vaccine. 33(32).

Malnourished children are at a greater risk of death from vaccine-preventable diseases

Findings of a systematic review evaluating the relationship between pneumonia and malnourishment found that severely malnourished children in developing countries had 2.5 to 15 times the risk of death. For children with moderate malnutrition, the risk of death ranged from 1.2 to 36.

Chisti, M.J., Tebruegge, M., La Vincente, S., et al.. 2009. Pneumonia in severely malnourished children in developing countries – mortality risk, aetiology and validity of WHO clinical signs: a systematic review. Tropical Medicine and International Health. 14(10).

Diarrhea is associated with pneumonia in undernourished children

In a recent review of data from developing countries, researchers found that episodes of diarrhea may predispose undernourished children to pneumonia.

Schlaudecker, E.P., Steinhoff, M.C. and Moore, S.R.. 2011. Interactions of diarrhea, pneumonia, and malnutrition in childhood: recent evidence from developing countries. Current Opinion in Infectious Diseases. 24(5).