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CDC urges flu vaccination for all, especially pregnant women

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Vaccination coverage is only around 50% for pregnant women



In an appeal for increased vaccination against influenza, the Centers for Disease Control and Prevention (CDC) announced that, although vaccination coverage has increased for some groups of the population, the nation needs to do better. Recommendations from the Advisory Committee on Immunization Practices reported seasonal influenza vaccination data in the CDC’s Morbidity and Mortality Weekly Report (MMWR) on September 20, 2013.1

More children aged 6 months through 17 years received the influenza vaccine during the 2012–2013 season (56.6%), up 5.1% from the 2011–2012 season. Smaller increases were reported for adults aged 18 years and older at 41.5%, up 2.7% from 2011–2012. Overall, 45% of the entire US population aged 6 months and older was vaccinated in 2012–2013. However, this falls short of public health goals.2

Howard K. Koh, MD, Assistant Secretary for Health at the US Department of Health and Human Services, pointed out that, although the increases in number of those who received the influenza vaccine last year is significant, there is more work to do. “Despite substantial progress, we can do even more to make our country healthier through prevention. Flu vaccination should represent a simple investment we make year in and year out to maximize the gift of health.”2

What vaccines will be available for the 2013-2014 season?
The 2013-2014 influenza vaccine is detailed in MMWR1:

For the upcoming influenza season, it is expected that trivalent live attenuated influenza vaccine (LAIV3) will be replaced by a quadrivalent LAIV formulation (LAIV4). Inactivated influenza vaccines (IIVs) will be available in both trivalent (IIV3) and quadrivalent (IIV4) formulations. Vaccine virus strains included in the 2013–14 US trivalent influenza vaccines will be an A/California/7/2009 (H1N1)–like virus, an H3N2 virus antigenically like the cell-propagated prototype virus A/Victoria/361/2011, and a B/Massachusetts/2/2012–like virus. Quadrivalent vaccines will include an additional influenza B virus strain, a B/Brisbane/60/2008–like virus, intended to ensure that both influenza B virus antigenic lineages (Victoria and Yamagata) are included in the vaccine.

Risk of complications from influenza
Vaccination to prevent influenza is particularly important for those who are at increased risk for severe complications from influenza. Pregnant and postpartum women are at higher risk for severe illness and complications from influenza than women who are not pregnant because of changes in the immune system, heart, and lungs during pregnancy.1

Increased severity of influenza among pregnant women was reported during pandemics in 1918–1919, 1957–1958, and 2009–2010. Severe infections were also observed among postpartum (within 2 weeks after delivery) women during the 2009–2010 pandemic.1

One study by Cox et al indicated an increase in delivery complications, including fetal distress, preterm labor, and cesarean delivery, for pregnant women with respiratory hospitalizations during the flu season.1

Vaccination coverage has increased in pregnant women in the last few years, but, unlike other groups where rates continue to increase, coverage in pregnant women appears to have stalled at around 50%.2

Pregnant women who were treated with antivirals more than 4 days after symptoms arose were more likely to be admitted to an ICU (57% vs 9%; 95% confidence interval [CI] 3.5–10.6] than those treated within 2 days on symptom onset.1

Infants. Pregnant women have protective levels of anti-influenza antibodies after vaccination that are passively transferred to their children. In a randomized controlled trial of vaccinated pregnant women who later breastfed their children, infants of vaccinated women had a 63% reduction in laboratory-confirmed influenza during the first 6 months of life. In addition, authors Zaman et al reported a 29% reduction in respiratory illness with fever among the infants and a 36% reduction in respiratory illness with fever among their mothers during the first 6 months after birth.1

Another study by Eick et al found that infants aged less than 6 months who were born to women who were given influenza vaccination during pregnancy had significantly reduced risk for influenza virus infection (relative risk [RR]: 0.59; 95% CI = 0.37–0.93) and hospitalization for influenza-like illness (ILI) (RR: 0.61; 95% CI = 0.45–0.84).1

Infants born to women with laboratory-confirmed flu during pregnancy did not have higher rates of low birthweight, congenital abnormalities, or lower Apgar scores compared with infants born to uninfected women.1

ACOG recommendations for pregnant and postpartum women

Because of the increased risk for serious illness and complications from influenza, the American College of Obstetricians and Gynecologists (ACOG) recommends that all women who are pregnant or who might be pregnant in the upcoming influenza season receive the IIV vaccine. This vaccination can be administered at any time during pregnancy, before and during the influenza season.3

LAIV is not recommended for pregnant women. Postpartum women can receive either LAIV or IIV. Pregnant and postpartum women do not need to avoid contact with persons recently vaccinated with LAIV.1


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