Maternal antibodies are however often suboptimal and consequently do not necessarily provide adequate protection to the infant Vaccines are among the most effective preventive tools available to date for reducing infectious diseases and their complications and sequelae. Maternal immunization has emerged as a promising intervention and offers an exceptional opportunity to protect pregnant women and their babies from diseases that cause substantial morbidity and mortality. During early life newborns are partially protected through placental transfer of maternal immunoglobulins. Maternal antibodies are however often suboptimal and consequently do not necessarily provide adequate protection to the infant. Vaccine-induced maternal antibodies are actively transferred from the mother to the foetus across the placenta providing passive protection to the foetus and neonate against vaccine-preventable diseases, particularly over the critical first few months of life before the infant´s shows the ability to respond to vaccines.
The negative impact of most diseases that can be prevented with vaccines in pregnancy is largely concentrated among mothers and infants from low and middle-income countries (LMICs). In these areas, antenatal care offers an excellent opportunity to achieve maximal protection with minimal contact, since in resource-poor settings opportunities to reach the population through the health system are limited. Therefore maternal immunization programs should be firmly embedded in antenatal care as this strategy would not only benefit both women and their infants but would also contribute to strengthen the existing health services. One of the major obstacles standing in the way to achieve this vision is the lack of reliable available evidence from LMICs on the burden of diseases that can be prevented through maternal immunization and on the safety and efficacy of vaccines in pregnant women. As a result, pregnant women and their babies do not have access to safe and effective products, which leads to a vicious cycle with no opportunities for the most vulnerable groups indeed. Currently inactivated influenza, tetanus toxoid and acellular pertussis vaccines are recommended during pregnancy. However, tetanus toxoid is the only widely implemented vaccine in low-income countries, and despite WHO recommendations, most countries in the developing world do not have national recommendations for influenza vaccines in pregnancy. No other vaccine is recommended during pregnancy in these contexts.
Thus quality data and stronger evidence -covering a variety of different geographical and epidemiological contexts- on the burden of diseases that can be prevented through maternal immunization and on the efficacy and safety of vaccines in pregnancy is a prerequisite to lay the ground for the future development of maternal immunization policies in LMICs. Throughout the next decade, these countries will be introducing new lifesaving vaccines into their routine immunization programs. Prioritising maternal immunization can trigger a decisive move to improve the health of women and children in a cost-effective, equitable and evidenced-based way.