Pregnant women are at particularly high risk for morbidity and mortality related to several vaccine-preventable diseases. Even though it's protective, only half of women get vaccinated with flu vaccine during pregnancy. What influences women from getting a flu vaccine? It’s the recommendation from their health care provider. Moms want her child to be better protected. Two recent papers discussed the protective nature of flu vaccination in pregnancy. Why are Moms more vulnerable? The hypothesis says that when a woman is pregnant, her immune system changes in order to increase immunotolerance from the newly coming antigens and also the respiratory system changes during the second and third trimester when the uterus starts pushing against the diaphragm and cardiovascular changes as well. These overall changes increase their chances of getting infected. Therefore, women during pregnancy are at increased risk of getting the flu and especially during a pandemic. It has been reported that pregnant women with H1N1 influenza were over 4 times more likely to be hospitalized than persons in general population. Statistically speaking, pregnant women make up to 1% of the general population. They accounted for about 5% of the 2009 H1N1 related deaths in the United States. Therefore, due to the vulnerable immune response during pregnancy, it is advised that pregnant women take influenza-related vaccines. Benefits to New Borns Young children are at particular risk for influenza-related complications. Babies who are less than 6 months of age have been shown to be at highest risk of being hospitalized and chances of death. Unfortunately, Babies less than 6 months are not eligible to receive influenza vaccines. So, they really depend on the passive protection from their mother i.e. the antibodies that are passed from their mother across the placenta to protect them from illness including influenza. So it's so important for moms to receive influenza vaccine during pregnancy. Passive immunity through breast milk comes through IgA antibodies. A couple of studies showed their beneficial effect. It decreases the risk of getting an infection. Apart from this, people around the baby should be vaccinated, that's one way of cocooning or protecting the baby before he/ she gets actively immunized. Safety of Vaccination during Pregnancy Randomized double-blind placebo-controlled clinical trial during pregnancy was done in South Africa during 2009-2012. It is the follow-up of the previous study where 1000 women received a flu vaccine and the other 1000 women received a placebo. Then they followed their babies up to 6 months of life, looking at about what's the likelihood of them getting influenza was. They looked at the antibodies in the blood. The first study demonstrated that women who received the flu vaccine during pregnancy had a decreased chance of having the flu as is the case with their babies until 6 months of life. The second study looked at the length of the protective window. They followed the babies at 1st, 2nd, 4th week and at 6 months. Protection is high for babies in first 8 weeks of life or younger (85.6%). It decreased in later ages to 25% (8-16 weeks) and 30% (16-24 weeks) of age due to the waning of antibodies. Time and type of vaccine for Moms Any time is the best time to get vaccinated for pregnant women, even before planning for a pregnancy. Moms should receive the inactivated influenza vaccine, as live vaccines are contraindicated during pregnancy. Though certain myths circulate around flu vaccines during pregnancy, studies showed the efficacy of inactivated vaccines. The risk to a developing fetus from vaccination of the mother during pregnancy is theoretical. No evidence exists of risk to the fetus from vaccinating pregnant women with inactivated virus or bacterial vaccines or toxoids. Live vaccines administered to a pregnant woman pose a theoretical risk to the fetus; therefore, live, attenuated virus and live bacterial vaccines generally are contraindicated during pregnancy. "Benefits of vaccinating pregnant women usually outweigh potential risks when the likelihood of disease exposure is high, when infection would pose a risk to the mother or fetus, and when the vaccine is unlikely to cause harm." Conclusion Pregnant women are at particularly high risk for morbidity and mortality related to several vaccine-preventable diseases. The benefits from receiving the influenza vaccine while pregnant are great. Influenza vaccine during pregnancy protects both the expectant mother and her unborn child from complications of influenza. A Canadian study showed that babies born to women vaccinated against influenza while pregnant were less likely to be born prematurely or have a low birth weight. Influenza vaccination during pregnancy also prevents influenza hospitalization in 9 out of 10 babies before they reach 6 months of age, the age when they can start to receive the vaccine themselves. This is due to the transfer of protective antibodies from the pregnant woman to the baby, which remains in the newborn’s blood for the first few months of life. Several other vaccines aimed at providing passive immunity to neonates are either currently recommended or in development. References: Nunes, Marta C., et al. (2016). Duration of infant protection against influenza illness conferred by maternal immunization: secondary analysis of a randomized clinical trial. JAMA pediatrics, 170(9), 840-847. Kerr, S. (2016). Influenza Vaccination Coverage During Pregnancy—Selected Sites, United States, 2005–06 Through 2013–14 Influenza Vaccine Seasons. MMWR. Morbidity and Mortality Weekly Report, 65. Legge A. et. al. (2014). Rates and determinants of seasonal influenza vaccination in pregnancy and association with neonatal outcomes. Canadian Medical Association Journal, 186: E157-64. CDC. General recommendations on immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 2011; 60 (No. 2): 26.
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