Influenza Vaccination Among Women with a Recent Live Birth

Pregnant Women and Influenza Vaccination

Pregnant women are at increased risk for severe illness from influenza because of physiological changes during pregnancy (1-3). Infants younger than 6 months of age also are at high risk of severe illness from influenza, but they are too young to be vaccinated (4). The best way to protect pregnant women from influenza is for them be vaccinated every year (5-6). Vaccination for influenza obtained while a woman is pregnant has also been shown to prevent influenza infection and influenza-related hospitalizations in her infant up to 6 months of age (6-8). The American College of Obstetricians and Gynecologists (ACOG) and the Advisory Committee on Immunization Practices (ACIP) recommend influenza vaccination for women who are or will be pregnant during influenza season, regardless of trimester (5,9). Prior to 2009, influenza vaccination levels among pregnant women were generally low (~15%) (5,9). During the 2009-10 influenza season, excess morbidity and hospitalization admission due to the influenza A(H1N1) pdm09 (pH1N1) pandemic virus were observed among pregnant women (10-12). Therefore, they were listed as an initial target group to receive pH1N1 influenza vaccination when supplies were limited. Besides the monovalent pH1N1 influenza vaccination, the usual inactivated trivalent seasonal influenza vaccination was also recommended for pregnant women during the 2009-10 influenza season (13). A previous study reported that influenza vaccination coverage among pregnant women increased substantially during the 2009-10 influenza season in response to the pH1N1 pandemic (14). This fact sheet summarizes overall and state-specific pH1N1 and seasonal vaccination coverage among pregnant women using data from states participating in the Pregnancy Risk Assessment Monitoring System (PRAMS).

PRAMS

PRAMS is an ongoing, population-based survey that collects data on a wide range of maternal behaviors and experiences before, during, and after pregnancy among women who recently delivered a live-born infant. The survey consists of monthly stratified random samples of 100-300 women with recent live-born infants sampled from the birth certificate registry of each participating state. The selected mothers are mailed a questionnaire 2-6 months after delivery, and those who do not respond by mail are contacted by telephone. During the 2009-10 influenza season, 29 states and New York City agreed to add a supplemental vaccination question module to their PRAMS survey. Questions about influenza vaccination were asked separately for seasonal and pH1N1 influenza vaccines, including whether the woman received a vaccination during her most recent pregnancy (including before pregnancy, during pregnancy, and postpartum); the month and year of vaccination; whether her health care provider recommended or offered her the vaccine; reasons for not receiving the vaccination, etc. Below is the list of related questions:

1. At any time during your most recent pregnancy, did a doctor, nurse, or other health care worker offer you an H1N1 flu shot or tell you to get one?
2. During your most recent pregnancy, did you get an H1N1 flu shot?
3. During what month and year did you get the H1N1 flu shot?
4. Where did you get your H1N1 flu shot?
5. What were your reasons for not getting the H1N1 flu shot during your most recent pregnancy?
6. At any time during your most recent pregnancy, did a doctor, nurse, or other health care worker offer you a seasonal flu shot or tell you to get one?
7. Since September 2009, did you get a seasonal flu shot?
8. During what month and year did you get the seasonal flu shot?
9. What were the reasons for not getting a seasonal flu shot during your most recent pregnancy?

This fact sheet includes previously published state-specific PRAMS data on seasonal and/or pH1N1 flu vaccination among women who had a live birth from September 1, 2009 through May 31, 2010 from 29 states and New York City (15), and new information on vaccination coverage among the combined 29 states and New York City by maternal age, race/ethnicity, Medicaid and private insurance status, WIC participation and provider recommendation for or offer of vaccination. Vaccination status was determined by the women’s responses to question 2 above regarding pH1N1 vaccination or to question 7 above regarding seasonal vaccination. Women who responded that they don’t know their vaccination status, refused to answer the vaccination questions, or had missing data regarding vaccination status were excluded from the analysis. We calculated vaccination coverage for seasonal vaccination (n=27,153), pH1N1 vaccination (n=27,372), either seasonal or pH1N1 vaccination (n=26,695), and for receipt of both vaccines (n=26,695).

Results

Table 1 shows the overall and state-specific seasonal, pH1N1, either seasonal or pH1N1, and both seasonal and pH1N1 influenza vaccination coverage. Table 2 shows the vaccination coverage by maternal age, race/ethnicity, Medicaid and private insurance status, WIC participation and provider recommendation for or offer of vaccination. State-specific seasonal and pH1N1 vaccination levels among the PRAMS participating states are shown in the maps in Figures 1 and 2. The state median response rate to the flu supplemental survey was 69.1% (range 53.7% to 85.0%).

Overall, 45.3% of pregnant women from the 29 states and New York City reported receiving vaccination for seasonal influenza, and state-specific estimates ranged from 26.1% (Florida) to 67.9% (Minnesota). For pH1N1, overall vaccination coverage was 38.8%, and state-specific estimates ranged from 21.9% (Mississippi) to 63.3% (Vermont) (Table 1, Figure 1). Overall, more than half of the women (56.8%) reported receiving either seasonal or pH1N1 influenza vaccine, with state estimates ranging from 38.9 (Florida) to 80.2 (Rhode Island); 27.3% reported receiving both of the vaccines, with state estimates ranging from 15.0% (Florida) to 49.9 % (Vermont) (Table 1).

Compared with older women, those under the age of 25 years had the lowest vaccination coverage for either seasonal or pH1N1 vaccines. With regard to race/ethnicity, Hispanic and non-Hispanic black women had the lowest vaccination levels compared to their counterparts. Vaccination coverage also was lowest among women who received Medicaid at delivery versus those that did not, among those without private insurance, and those who participated in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) (Table 2).

About 61% of women who reported that their health care provider recommended or offered the seasonal influenza vaccine received it, which was more than five times the coverage among those who didn’t receive a provider recommendation/offer. Similarly, for pH1N1, the prevalence of obtaining a vaccination among those who received a provider recommendation/offer was about three times higher than among those who didn’t receive a provider offer/recommendation (Table 2).

Summary

Although these PRAMS data reflect influenza vaccination that was obtained before, during, or after pregnancy, they suggest that vaccination coverage is well below the Healthy People 2020 target for 80% of pregnant women to be vaccinated against seasonal influenza (16). The PRAMS data also suggest that health care providers played an important role in increasing vaccination coverage in this population; however, many women who were vaccinated reported that their health care provider did not offer or did not recommend vaccination. Continued efforts are needed to encourage health care providers to follow guidelines in recommending and offering influenza vaccination to their pregnant and postpartum patients.

State-specific vaccination coverage varied widely from state to state with generally lower vaccination prevalence in southern states and higher prevalence in northeastern states. Further research is needed to identify vaccination-related best practices at the state and local levels. Partnerships between various stakeholders at the local, state, and federal levels will be necessary to promote increased implementation of evidence-based strategies (17) and ensure the achievement of the Healthy People 2020 target that 80% of pregnant women will be vaccinated against seasonal influenza (16).

Additional Resources

• Pregnancy Risk Assessment Monitoring System (PRAMS)
• Healthy People 2020 objective IID-12.10 for seasonal influenza vaccination among pregnant women
• Text 4 baby
• Flu vaccination accepted by pregnant women not linked with miscarriage

References

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2. Neuzil KM, Reed GW, Mitchel EF, et al. Impact of influenza on acute cardiopulmonary hospitalization in pregnant women. Am J. Epidemiol. 1998;148(11):1094-1102.
3. Jamieson D, Theiler R, Rasmussen S. Emerging infections and pregnancy. Emerging Infectious Disease. 2006;12:1638-1643.
4. Poehling KA, Edwards KM, Weinberg GA, et al. The underrecognized burden of influenza in young children. N Engl J Med 2006; 355:31-40.
5. CDC. Prevention and control of influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices (ACIP), 2010. MMWR Morb Mortal Wkly Rep 2010;59(No. RR-8).
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8. Zaman K, Roy E, Arifeen SE, et al. Effectiveness of maternal influenza immunization in mothers and infants. N Engl J Med 2008; 359:1555-64.
9. American College of Obstetricians and Gynecologists Committee on Obstetric Practice. Influenza vaccination and treatment during pregnancy. Obstet Gynecol 2004;104(5 pt 1):1125-6.
10. Jamieson DJ, Honein M, Rasmussen SA, et al. Novel influenza A (H1N1) pregnancy workgroup: H1N1 2009 influenza virus infection during pregnancy in the USA. Lancet 2009; 374:451-8.
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12. Centers for Disease Control and Prevention. 2009 pandemic influenza A (H1N1) in pregnant women requiring intensive care–New York City, 2009. MMWR Morb Mortal Wkly Rep 2009; 59:321-6.
13. Centers for Disease Control and Prevention. Use of influenza A (H1N1) 2009 monovalent vaccine: recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009. MMWR Morb Mortal Wkly Rep 2009; 58(early release):1-8.
14. Ding H, Santibanez TA, Jamieson DJ, et al. Influenza vaccination coverage among pregnant women---National pH1N1 Flu Survey (NHFS). Am J Obstet Gynecol 2011;204(6 Suppl 1):S96-106.
15. CDC. Influenza Vaccination Coverage Among Pregnant Women — 29 States and New York City, 2009–10 Season. MMWR Morb Mortal Wkly Rep 2012; 61(07);113-118.
16. Healthy People 2020 objectives for influenza vaccination among pregnant women.
17. CDC. The Guide to Community Preventive Services, Vaccinations to Prevent Diseases, Community Guide Systematic Reviews. Accessed September 24, 2011.