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Immunology 101 Series: To Keep You and Your Baby Safe, Vaccines Are Expected When You’re Expecting

By Aimee Pugh-Bernard, PhD

True or False? A developing baby acquires protection against infectious diseases from its mother during pregnancy. TRUE! The immunizations a mother-to-be receives before and during pregnancy can help protect her newborn baby from some infectious diseases during the first few months of life.

In the eighth installment of the Immunology 101 Series, Aimee will explain the science behind immunization and pregnancy.

Vaccines allow for the transfer of protection from mother to developing baby
During pregnancy the mother transfers protective antibodies made by her own immune system to the developing baby. This ‘passive’ transfer of antibody between mother and baby can help protect the newborn baby upon arrival in the outside world for the first few months of life*. When a mother receives recommended vaccines before and during pregnancy, she provides protection for her baby before and after birth. Antibodies, also called immunoglobulins, are proteins made by B cells, a specialized cell of the immune system, in response to pathogen. One of the five forms of antibody, immunoglobulin G or IgG, can pass through the placenta into the baby during pregnancy. This form of antibody – IgG – is produced most commonly after an immune response to vaccines. The vaccines recommended by your doctor just before and during pregnancy will result in the best possible protection against infectious diseases for mother and baby.

Before pregnancy
Any woman planning to become pregnant should be up-to-date on adult immunizations for the best possible protection for her and her baby. Some forms of vaccines should be administered before pregnancy, and others are recommended during pregnancy. These recommendations depend on the type of the vaccine or the way it was made. The types of vaccines that are recommended before pregnancy, but not during, are live vaccines. Live vaccines are made with living pathogens that have been attenuated or weakened to the point that they will not cause disease but will produce an immune response (or training of the immune system) that results in immune memory and long-lasting protection.

An example of a vaccine that should be given before pregnancy is the measles, mumps and rubella (MMR) vaccine. With the recent outbreaks in measles across the country, it is especially important make sure women are up-to-date on their MMR vaccinations before becoming pregnant.

During Pregnancy
The types of vaccines that are recommended during pregnancy are made of non-living components of pathogen, these include the Tdap and the shot form of the flu vaccine.

Tdap
An example of a vaccine that should be given during pregnancy, between 27 and 36 weeks gestation, is the Tdap, which protects against pertussis (also called ‘whooping cough’) as well as diphtheria and tetanus. Whooping cough is caused by a bacteria called pertussis that spreads very easily, especially from mother to newborn. Babies infected with pertussis often cough uncontrollably, which can cause them to stop breathing. The vaccine is given during pregnancy in order to allow antibody transfer from mother to baby through the placenta. This protection can last for up to three months in the newborn, which is when infants are most vulnerable to severe disease and complications from pertussis. Tdap vaccination during pregnancy is important because babies cannot be vaccinated with DTaP (the child form of Tdap) until they’re two months old and do not have full protection until six months of age after they’ve received all three doses of DTaP.

Flu
Another example of a vaccine that should be given during pregnancy is the inactivated or shot form of the flu vaccine. The nasal spray form of the flu vaccine is made with live, attenuated virus and should not be given during pregnancy.

If you are planning to become pregnant, but are not yet pregnant during flu season when the vaccine is available, it would be a good idea to get the shot just to be safe. If you are pregnant during flu season, the inactivated shot form of the flu vaccine can safely be given during any trimester of pregnancy.

The administration of the flu vaccine is very important, as babies younger than 6 months of age are considered too young to receive the flu vaccine and will rely on antibodies transferred from the mother during gestation for the first several months of life to maintain immunity against the influenza virus.

The administration of the flu vaccine is also incredibly important in relation to the pregnant woman. Beyond gaining weight, pregnant women undergo many changes to their body. Many of these normal changes that occur during pregnancy can make them more prone to severe illness from infectious diseases such as the flu. As an example, a pregnant woman’s immune system is weakened in order for her body to maintain the pregnancy. Pregnant women also experience changes to the heart and lungs due to an increased amount of blood in circulation. These normal, physiological changes associated with pregnancy make pregnant women more prone to severe illness from infectious diseases. Infection with the flu virus also poses a risk to unborn babies, including premature labor and delivery and/or miscarriage/stillbirth. Getting vaccinated annually is a safe way to protect mom and baby from the flu.

Quick Review_IZ and PregnancyAdditional vaccines
A woman’s healthcare provider may also recommend additional vaccines before, during and after pregnancy to help protect her and her baby. A baby born to a mother infected with hepatitis B is at very high risk for becoming infected with hepatitis B during delivery, as this virus is spread through contact with bodily fluids and blood. In this case, a vaccine against hepatitis B may be recommended during pregnancy. A vaccine against hepatitis A may be recommended if the mother has a history of chronic liver disease. The meningococcal vaccine may be recommended if the mother may be exposed to meningococcal disease through work or travel. It is best to consult with a doctor or healthcare professional to discuss immunization recommendations before, during and after pregnancy.

After pregnancy
After baby has arrived, the CDC recommends new mothers help protect their child from exposure to diseases such as measles, mumps and rubella (MMR), varicella (chickenpox), tetanus, diptheria and pertussis (Tdap) and influenza by getting vaccinated against these diseases (if not already vaccinated) before leaving the hospital. It is safe and beneficial to both mom and baby for mothers to receive vaccines after birth, even when breastfeeding.

A mother who breastfeeds her baby passively transfers antibodies in breast milk to her child. Although this is one way of protecting a newborn baby against infectious disease it is still very important to immunize newborn babies according to the recommended immunization schedule. Most people don’t know that the antibodies transferred in breast milk primarily remain in the intestines or gut and are not absorbed into the bloodstream. This means that the antibodies in a mother’s breast milk do not enter the blood where they are most needed to protect against infectious diseases that circulate in the blood. Examples of infectious diseases that circulate in the blood are numerous and include measles, pertussis (whooping cough), varicella (chickenpox), polio and many others. For the best possible protection it is a good idea to breast feed and immunize newborn babies according to the recommended immunization schedule.

It is also important for adults and adolescents who have regular contact with your newborn to be vaccinated against diseases such as influenza and pertussis. Doing so can help surround the infant with a blanket or “cocoon” of protection against the disease until baby is old enough to be immunized.

For more information, check out these helpful resources:

  • Immunizations & Pregnancy (PDF)CDC IZ and Pregnancy flyer – Centers for Disease Control and Prevention (CDC)
    This handy chart shows which vaccines are recommended before, during or after pregnancy.
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