Although dengue, a viral infection transmitted through mosquito bites, threatens the health of “about half of the world’s population”, there has been little investigation into the links between infection in pregnancy and worse birth outcomes. However, researchers published a paper in American Economic Journal: Applied Economics providing the “first causal evidence” of the effect that dengue has on “several measures of health at birth” and longer-term health outcomes.
As dengue has been poorly understood and has produced an “uncertain evidence base” it is not considered within the category of TORCH infections. These are the congenital infections of toxoplasmosis, others, rubella, Cytomegalovirus, and herpes simplex. Consequently, it is not described as a “maternal infection of concern” and is largely overlooked by antenatal health advice. In this study, the authors present their case for the inclusion of dengue in the list.
Dengue has “relatively low mortality” but a “substantial economic burden” through combined direct pressures on healthcare services and indirect consequences of infection. The authors suggest that climate change is bringing the vector, the Aedes mosquito, outside its traditional breeding ground of tropical and subtropical regions. Dengue is now endemic in over 100 countries. A flavivirus, dengue can range from subclinical infections to severe flu-like symptoms. Although infection with one strain is understood to provide lifelong immunity to that strain, there are several serotypes, which complicate the development of effective vaccines.
What does the study show?
The study is focused on the Southeastern Brazilian state of Minas Gerais. It is the “second most populous state in Brazil” and has an incidence of infections “representative of the average incidence across Brazil”. It also presented a useful case study because of the availability of “high-quality linked administrative records”.
The findings demonstrate the tangible consequences of dengue infection; in-utero dengue “reduces BW by about 27 grams on average”. This effect is exaggerated for infants at the lower end of the birth weight scale, increasing by 15%, 67%, and 133% for low, very low, and extremely low birth weights. Furthermore, the authors examined the effects on longer-term measures of child health, through an investigation of birth records with mortality and hospitalisation records.
“We find that maternal dengue during pregnancy increases the risk of hospitalisation of children substantially; maternal dengue leads to a 27% increase in hospitalisations over a three-year period after birth.”
The effects are “long-lasting” and cause substantial increases in medical expenditures related to hospitalisation in the first two years after birth.
What does this mean?
The authors claim that their paper emphasises the “devastating impact” of maternal dengue infections on newborns’ health. As dengue continues to spread throughout Brazil and other countries, they estimate that “more than half of the world’s unborn children” are “at risk of lasting damage to their health”.
From an economic perspective, the authors believe that investment in dengue prevention and treatment is worthwhile, as vaccines are developed, and preventative measures considered. Dr Martin Foureaux Koppensteiner, co-author from the University of Surrey, commented that this “compelling evidence” emphasises the need for “increased awareness, prevention, and targeted interventions”.
“Including dengue fever in [the TORCH list] will ensure that pregnant women are aware of the risks involved with infections during pregnancy and can take precautions.”
Co-author Dr Livia Menezes from the University of Birmingham agrees that their work should be used by public health officials to encourage vaccine development.
“This study not only deepens our understanding of the consequences of dengue infections during pregnancy, but also serves as a call to action for policymakers, healthcare professionals, and global communities to prioritise preventative measures and support affected families.”
This study highlights the importance of accelerating the development of effective vaccines, particularly for use in pregnancy. However, we recently heard from Takeda that it had “voluntarily withdrawn” the US Biologics License Application for TAK-003 after “discussions” with the US FDA on “aspects of data collection.
TAK-003 is already approved in several countries but will be “further evaluated” for US application. Dr Gary Dubin, president of Takeda’s Vaccines Business Unit, commented that the clinical programme was “designed to account for the complex global nature of dengue”.
“The urgent global need to combat the growing burden of dengue remains, and we will continue to progress regulatory reviews and provide access for people living in and traveling to dengue-endemic areas while we work to determine next steps in the US.”
We are looking forward to exploring preventative measures to infectious diseases such as dengue at the World Vaccine Congress in Barcelona this October. Will you join us there? Don’t forget to subscribe to our weekly newsletter for more like this.