Immunization Guide: Immunological Aspects of Maternal Vaccination

Content

● Introduction (see). ● Immunological aspects of maternal immunization (see). ● Immune system of mother and fetus (see). ● The influence of maternal vaccination on the immune system in the first years of life (see) | Transfer of maternal antibodies through the placenta and breast milk | Possible interference of maternal antibodies in childhood vaccination: effect dullness (see) | Transfer of maternal cells across the placenta (see). ● Key points (see). ● Additional information on this website, bibliographical references and recommended references (see).

In a nutshell

● The chapter has been revised and updated. 48 AEP’s online immunization manual on the immunological aspects of maternal immunization. ● All sections have been reviewed and bibliographical references and recommended references have been updated. ● This note examines the maternal and fetal immune systems and the impact of maternal vaccination in the early years of life through the transfer of maternal antibodies and cells.

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Introduction

AEP’s online immunization guidance continues to be updated. In this case, it was Chapter 48 on the immunological aspects of immunization, which emphasized updating the sections dealing with maternal immunization.

All sections have been reviewed and bibliographical references and recommended references have been updated. Included news about vaccination of children against covid for our country. This note summarizes the most noteworthy aspects of the update to this chapter. Both the chapter itself and this review, as well as the image accompanying this note, are the work of an immunologist. Jose Gomez Rialwho is grateful for your cooperation.

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Immunological aspects of maternal immunization

newborn immunization This poses a challenge in terms of preventing infections that can be prevented by immunoprophylaxis, due to the greater risk of contracting infections because their immune system is unable to mount an effective protective response, and because of the very small number of vaccines authorized in the early days life.

maternal immunization It is a highly effective public health strategy to protect mothers, fetuses and infants from certain infections. Newborn protection is based on Transfer of maternal antibodies and maternal immune cells across the placenta and breast milk.. The required antibody concentration for effective protection, the optimal timing of vaccination, and the possible interference of maternal antibodies with subsequent vaccinations are still under study.

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Immune system of mother and fetus

Maternal immune system and maternal-fetal interaction:

• During pregnancy, the mother’s immune system undergoes changes to ensure the survival and development of the fetus. These changes are associated with immunomodulation rather than immunosuppression.
• During pregnancy, the maternal immune barrier against infection uses a combination of immune signals and modulators originating from the feto-placental dyad, including the placenta and decidua. During the second trimester, the mother’s immune system protects the fetus by passively transferring maternal antibodies (IgG isotype) and maternal immune cells across the placenta.

Immune system of the fetus and newborn:

• The fetal immune system begins to develop after the first weeks of intrauterine life. During the second trimester, the number of immune cells increases, matures and differentiates. By the end of the third trimester, the fetal immune system is functioning and capable of responding. At birth, the newborn’s innate response is characterized by the production of certain cytokines that may influence susceptibility to viral infections and response to vaccines.
• Exposure to antigens from birth promotes further adaptation of the child’s immune system. B and T cells are present in abundance at birth but gradually decline until adulthood.

Maternal immunization is an effective way to reduce the risk of disease in the mother, fetus, and infant.

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The effect of maternal vaccination on the immune system in the first years of life

Transfer of maternal antibodies through the placenta and breast milk.

• Maternal immunization during pregnancy increases the amount of specific antibodies produced as a result of vaccination, protecting both mother and baby in the first months of life. The transfer of maternal antibodies across the placenta is dependent on the neonatal Fc receptor (FcRn) expressed on the syncytiotrophoblast. IgG antibodies are selectively transported from maternal blood to the fetus via FcRn. Placental transfer of IgG increases as pregnancy progresses, and the efficiency of transfer depends on the affinity of the IgG subtype for FcRn, with IgG1 being the subtype with the highest transfer.
• Previous maternal infections may also affect antibody transfer. Breastfeeding provides another protective mechanism as breast milk contains secretory IgA (sIgA), IgG and IgM, which provide the newborn with immunological benefits such as protection against gastrointestinal and respiratory pathogens. Breast milk also contains immune cells that can modulate the baby’s immune system. There are studies that have demonstrated the presence of vaccine-specific sIgA in the breast milk of vaccinated women during pregnancy, suggesting a protective role against respiratory diseases in infants.

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Possible interference of maternal antibodies in childhood vaccination: effect dullness

The influence of maternal IgG antibodies on the humoral response to vaccines administered in the first months of life is of concern: the presence of maternal antibodies may reduce antibody production in infants following vaccination, thereby affecting the child’s protection. This is known as dullness and may be associated both with antibodies transmitted by the mother to the fetus and with antibodies produced in response to natural infection during pregnancy. However, there are studies that have shown conflicting results and their actual clinical significance is unknown. Studies conducted in countries such as the US and UK where maternal Tdpa vaccination was carried out found no evidence of a clinically significant effect. Finally, maternal antibodies do not appear to influence the infant’s cellular immune response following primary vaccination.

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Transfer of maternal cells across the placenta

The transfer of maternal cells across the placenta during pregnancy can affect the fetal immune system. It has been found that maternal infection or vaccines can influence infants’ immune responses to pathogens and vaccines after birth. Although it is unclear how the fetal immune system is trained without fetal infection, it is thought that vertical transfer of antigens from mother to fetus and the presence of maternal cells in fetal tissue may play a key role. This phenomenon is known as microchimerism and may promote feto-maternal tolerance and improve outcomes in future pregnancies. Besides, microchimeric cells Maternal cells can generate fetal regulatory T cells, which suppress fetal T cell functions and prepare the fetal immune system to resist pathogens after birth. The presence of fetal memory T cells has also been observed in uninfected infants born to infected mothers, suggesting that the fetal immune system may respond to maternal exposure to pathogen antigens. Maternal vaccinations during pregnancy may affect the development of the fetus’ innate immune system and its ability to fight infections. The timing of maternal vaccination may influence the transmission of vaccine antigens to the fetus and its subsequent immune response.

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Key points

• Maternal immunization protects the newborn in the early postpartum period, when the risk of infections is highest.
• Maternal antibodies are transmitted in the last months of pregnancy through the placenta (mainly IgG) and after birth during breastfeeding (mainly IgA).
• The presence of maternal immune cells has been demonstrated (microchimerism) in the blood of the fetus, which will provide a training function to neonatal immune cells.
• We have a variety of vaccines available for use in pregnant women with excellent demonstrated safety and effectiveness profiles.

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More information on this website

Bibliographical references and recommended references

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