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Breastfeeding and pneumonia

Pneumonia is one of the major causes of childhood mortality, accounting for 1.4 million deaths under the age of 5 years in 2010.[1] The majority of these deaths occur in developing countries.[2] However, an intervention as simple and low-cost as breastfeeding may substantially reduce this mortality burden. Feeding practices for young infants have an important impact on health outcomes. In particular, infants who are exclusively breastfed have fifteen times less chance of dying of pneumonia than infants who are not breastfed.[3] Besides protection from disease, breastfeeding is also associated with other positive outcomes, ranging from better cognitive development, educational performance, nutritional status and more.[4]

The beneficial effects of breast milk are well recognized by international health organizations and in the public health community. Evidence supporting the advantages of breastfeeding has increased over the past years. The World Health Organization (WHO) recommends starting exclusive breastfeeding within one hour after birth and throughout the first six months of life. Furthermore, WHO recommends continuation of breastfeeding with complementary food up to two years of age and beyond.[5] An increase of breastfeeding practices worldwide would significantly reduce childhood morbidity and mortality.

Antibodies in breast milk

We had the chance to study breast milk samples from a unique cohort of postpartum women from a maternal vaccine trial conducted in the rural Sarlahi region in Nepal. More than 3,500 pregnant women were enrolled in a maternal influenza vaccine trial between 2011 and 2013.[6] Both mothers and their infants were tested for respiratory syncytial virus (RSV) throughout the first six months postpartum by taking nasal swabs at any moment of respiratory illness. We developed a tool to measure antibodies in breast milk. The research question was whether mothers of infants who become sick in the first months of life have lower levels of antibodies in breast milk than mothers of infants who stay healthy. If this is the case, then antibodies in breast milk may be a mechanism via which maternal vaccines could protect young infants, in addition to well characterized antibody transfer across the placenta.

An intervention as simple and low-cost as breastfeeding may substantially reduce the mortality burden in developing countries

RSV infection is the second biggest cause of death in the infant period, second only to malaria. More than 99% of the mortality occurs in the developing world.[7] Currently, a maternal RSV vaccine is being tested in phase III clinical trials, and other promising candidates are also in clinical development. The transfer of antibodies against RSV via the placenta has been studied in different populations. However, it is essential to understand whether antibodies against RSV also protect the neonate via breast milk after birth.

Maternal vaccination

Maternal vaccination has emerged as a promising health intervention to combat infant morbidity and mortality among children too young to be vaccinated.[8] Several maternal vaccines are already being implemented for different diseases. For example, since 1999 maternal tetanus toxoid vaccination has been a very effective intervention to eliminate maternal and neonatal tetanus.[9] In 2012, WHO proclaimed that pregnant women are the highest-priority group for receiving influenza vaccination.[10] Maternal pertussis vaccination is implemented in several countries including the United States, the United Kingdom and Belgium. In addition, several vaccines are in development for implementation in pregnant mothers including maternal vaccines for Group B Streptococcus (GBS), respiratory syncytial virus (RSV), herpes simplex virus (HSV), congenital cytomegalovirus (CMV), and hepatitis E virus. Whereas maternal vaccines against GBS and RSV primarily aim to protect the infant from infection after birth, vaccines against HSV and CMV target women before conception, as primary infection during pregnancy is associated with poor foetal outcomes. Maternal vaccination boosts the levels of naturally occurring antibodies in the mother, allowing for greater transfer of protective immunity to the infant.

Protecting the newborn and the infant

In conclusion, current immunization schedules around the world are saddled with an immunity gap in the first months of life, a period when infants are also vulnerable to infectious diseases. Maternal immunization may be a key tool in allowing vaccination schedules to bridge this gap by passively immunizing the newborn via the mother. Breast milk plays a key role in protecting young infants from infectious diseases and may also play a role in the protection conferred from maternal vaccination.

Natalie Mazur working in the University of Washington Harborview Medical Center laboratory after receiving a KNAW (Dutch Academy for Medical Sciences) ter Meulen scholarship.

References

  1. Liu L, Johnson HL, Cousens S, Perin J, Scott S, Lawn JE, et al. Global, regional, and national causes of child mortality: an updated systematic analysis for 2010 with time trends since 2000. Lancet. 2012 Jun 9;379(9832):2151-61.
  2. Gupta GR. Tackling pneumonia and diarrhoea: the deadliest diseases for the world’s poorest children. Lancet. 2012 Jun 9;379(9832):2123-4.
  3. Lamberti LM, Zakarija-Grkovi I, Fischer Walker CL, Theodoratou E, Nair H, Campbell H, et al. Breastfeeding for reducing the risk of pneumonia morbidity and mortality in children under two: a systematic literature review and meta-analysis. BMC Public Health. 2013;13 Suppl 3 (Suppl 3):S18.
  4. Breastfeeding | Nutrition | UNICEF [Internet]. [cited 2018 May 7]. Available from: https://www.unicef.org/nutrition/index_24824.html
  5. WHO Breastfeeding. WHO. 2017;
  6. Tielsch JM, Steinhoff M, Katz J, Englund JA, Kuypers J, Khatry SK, et al. Designs of two randomized, community-based trials to assess the impact of influenza immunization during pregnancy on respiratory illness among pregnant women and their infants and reproductive outcomes in rural Nepal. BMC Pregnancy Childbirth. 2015 Dec 20;15(1):40.
  7. Nair H, Nokes DJ, Gessner BD, Dherani M, Madhi S a, Singleton RJ, et al. Global burden of acute lower respiratory infections due to respiratory syncytial virus in young children: a systematic review and meta-analysis. Lancet. 2010 May 1;375 (9725):1545-55.
  8. Omer SB. Maternal Immunization. N Engl J Med. 2017 Mar 30;376(13):1256-67.
  9. Chu HY, Englund JA. Maternal immunization. Clin Infect Dis. 2014 Aug 15:59(4):560-8.
  10. WHO SAGE Meetings. WHO. 2012;