The burden of vaccine-preventable diseases in pregnancy in low-resource settings
Authors: Azucena Bardají, Mark Steinhoff, Eusebio Macete, Teresa Aguado, Clara Menéndez
Journal: The Lancet Global Health (2016)

Substantial gains have been made globally for many of the Millennium Development Goals health targets, but progress in the improvement of health has been unequal with respect to the most vulnerable populations, and major discrepancies persist across regions and socioeconomic status. Maternal immunisation is a unique opportunity to improve maternal and infant health. Vaccines are one of the most successful interventions to protect pregnant women and their fetuses and infants from diseases that cause substantial morbidity and mortality.1Bratton KN Wardle MT Orenstein WA Omer SB Maternal influenza immunization and birth outcomes of stillbirth and spontaneous abortion: a systematic review and meta-analysis.Clin Infect Dis. 2015; 60: e11-e19Crossref Scopus (97) Google Scholar, 2Chu HY Englund JA Maternal immunization.Clin Infect Dis. 2014; 59: 560-568Crossref PubMed Scopus (99) Google Scholar However, pregnant women have been systematically left out of vaccine research, which limits the availability of safety and efficacy data in pregnancy and, consequently, reduces the access of this special population to effective treatment.2Chu HY Englund JA Maternal immunization.Clin Infect Dis. 2014; 59: 560-568Crossref PubMed Scopus (99) Google Scholar Data describing the burden and impact of infections in pregnancy, a period that is unique in presentation and outcome because of the altered physiology, is incomplete and poor.3Sobanjo-Ter Meulen A Abramson J Mason E et al.Path to impact: a report from the Bill and Melinda Gates Foundation convening on maternal immunization in resource-limited settings; Berlin—January 29–30, 2015.Vaccine. 2015; 33: 6388-6395Crossref PubMed Scopus (22) Google Scholar A complete understanding of the epidemiology of common pathogens such as group B streptococcus, respiratory syncytial virus, Bordetella pertussis, and influenza virus, which can be prevented through maternal immunisation, is a priority.3Sobanjo-Ter Meulen A Abramson J Mason E et al.Path to impact: a report from the Bill and Melinda Gates Foundation convening on maternal immunization in resource-limited settings; Berlin—January 29–30, 2015.Vaccine. 2015; 33: 6388-6395Crossref PubMed Scopus (22) Google Scholar Little is known about the prevalence of these infections in pregnancy, and accurate information about the illness incidence, its severity, and outcomes is often unavailable. Rigorous data collection and adequate clinical and epidemiological surveillance systems are needed for neonates, young infants, and pregnant women.4Shi T McLean K Campbell H Nair H Aetiological role of common respiratory viruses in acute lower respiratory infections in children under five years: a systematic review and meta-analysis.J Glob Health. 2015; 5: 010408Crossref Scopus (132) Google Scholar To what extent these pathogens contribute to maternal morbidity and mortality, and how much the infections determine fetal development and perinatal and infant survival, are unresolved questions. This information is especially needed from low-income countries, where the shortage of data is particularly manifest.5Feikin DR Ope MO Aura B et al.The population-based burden of influenza-associated hospitalization in rural western Kenya, 2007–2009.Bull World Health Organ. 2012; 90: 256-263ACrossref Scopus (27) Google Scholar, 6Madhi SA et al.Influenza vaccination of pregnant women and protection of their infants.N Engl J Med. 2014; 371: 2340Crossref Scopus (401) Google Scholar Adequate information about the burden of vaccine-preventable diseases in pregnancy is needed for several reasons: to understand the need for and to advocate for such vaccines,7Steinhoff M MacDonald N Pfeifer D Muglia LJ Influenza vaccine in pregnancy: policy and research strategies.Lancet. 2014; 383: 1611-1613Summary Full Text Full Text PDF PubMed Scopus (33) Google Scholar to monitor the success of their implementation, for vaccine optimisation, and to improve policy recommendations. Certainly, lessons can be learnt from the universal tetanus vaccine strategy, which did not necessitate broad burden information because the effect was clinically evident, or the case of the influenza vaccine, for which substantial evidence arose from several pandemics; in the 2009 influenza A (H1N1) epidemic, pregnant women were 7·2 times more likely than non-pregnant women to get admitted to hospital.8Creanga AA Johnson TF Graitcer SB et al.Severity of 2009 pandemic influenza A (H1N1) virus infection in pregnant women.Obstet Gynecol. 2010; 115: 717-726Crossref PubMed Scopus (278) Google Scholar Rigorous and robust burden data will be indispensable for making the case for new vaccines against pathogens such as group B streptococcus, respiratory syncytial virus, and B pertussis, about which little is known. Additionally, the role of diseases that are highly prevalent in some areas, such as malaria and HIV, in modifying the burden and in generating adequate immune responses to vaccines during pregnancy is important to understand. Placental damage caused by these comorbidities, especially malaria, might have a role in reducing antibody transfer across the placenta.9Moro L Bardají A Nhampossa T et al.Malaria and HIV infection in Mozambican pregnant women are associated with reduced transfer of antimalarial antibodies to their newborns.Infect Dis. 2015; 211: 1004-1014Crossref Scopus (30) Google Scholar, 10Naniche D Serra-Casas E Bardají A Reduction of antimalarial antibodies by HIV infection is associated with increased risk of Plasmodium falciparum cord blood infection.J Infect Dis. 2012; 205: 568-577Crossref Scopus (15) Google Scholar Collaborative work between research institutions in low and middle-income countries with long track records in conducting biomedical research at the highest quality standards will be instrumental to achieve this goal. These institutions offer the necessary research facilities and infrastructure to generate robust evidence from limited resource settings and to transform the data into interventions with direct benefits for the population.11Whitworth J Kokwaro G Kynyanjui S et al.Strengthening capacity for health research in Africa.Lancet. 2008; 372: 1590-1593Summary Full Text Full Text PDF PubMed Scopus (160) Google Scholar Examples of collaborative work, leading to excellent data gathering and documentation of the burden in low-resource settings, illustrate their added value in disease burden determination and potential for translation into policies.12Kotloff KL Nataro JP Blackwelder WC et al.Burden and aetiology of diarrhoeal disease in infants and young children in developing countries (the Global Enteric Multicenter Study, GEMS): a prospective, case-control study.Lancet. 2013; 382: 209-222Summary Full Text Full Text PDF PubMed Scopus (2261) Google Scholar Likewise, partnerships that bring maternal and infant health experts together with the vaccine and immunisation communities are crucial.3Sobanjo-Ter Meulen A Abramson J Mason E et al.Path to impact: a report from the Bill and Melinda Gates Foundation convening on maternal immunization in resource-limited settings; Berlin—January 29–30, 2015.Vaccine. 2015; 33: 6388-6395Crossref PubMed Scopus (22) Google Scholar Major gains can be obtained from the expertise of maternal health programmes in understanding the health problems affecting mothers and their infants, and the determinants of success and failure of interventions delivered through the antenatal care platform. In the next decade, low-income and middle-income countries will be introducing new life-saving vaccines into their routine immunisation programmes. Maternal immunisation has a tremendous potential to improve the health of infants during their most vulnerable stages of life. A comprehensive picture of the real burden of vaccine-preventable diseases in pregnancy is a necessary step for a successful maternal immunisation strategy and for the development of maternal immunisation policies in high-burden settings.