Jump in Influenza Immunization Rates Among Pregnant Women

Megan Brooks

December 03, 2010

December 3, 2010 — Seasonal and H1N1 influenza vaccination coverage rates among pregnant women in the United States were higher during the 2009 to 2010 season than in past influenza seasons, federal health officials at the US Centers for Disease Control and Prevention (CDC) in Atlanta reported Friday in the Morbidity and Mortality Weekly Report.

Combined data from 10 states show that the median trivalent seasonal influenza vaccination rate for 2009 to 2010 for pregnant women was 50.7% (95% confidence interval [CI], 48.9% - 52.4%). For the H1N1 vaccine, it was 46.6% (95% CI, 44.7% - 48.4%).

For comparison, seasonal vaccination rates were 24.2% during the 2007 to 2008 flu season and 11.3% during the 2008 to 2009 season.

The CDC believes several factors played a role in boosting last year's coverage rates among pregnant women; namely:

  • increased educational efforts aimed at providers and the general public,

  • designation of pregnant women as a high-priority group to receive influenza vaccine,

  • extensive public and private sector collaboration to implement the 2009 H1N1 vaccination campaign,

  • media attention to the 2009 H1N1 pandemic, and

  • making 2009 H1N1 vaccine available at no cost to providers.

It is currently recommended that all pregnant women be vaccinated for seasonal influenza during any trimester of pregnancy. In 2009, a novel strain of influenza A (H1N1) virus emerged, and pregnant women were found to be at greater risk for influenza-related complications from this new virus. As a result, the H1N1 vaccine was also recommended for pregnant women.

Pregnancy Risk Assessment Monitoring System Data Analysis

To estimate influenza vaccination coverage among pregnant women during the 2009 to 2010 season, the CDC turned to the Pregnancy Risk Assessment Monitoring System (PRAMS).

PRAMS is an ongoing, state-specific, population-based surveillance project collecting self-reported information on maternal attitudes and experiences before, during, and after delivery of a live infant. Supplemental questions were added to the PRAMS survey to gauge seasonal and 2009 H1N1 influenza vaccination coverage among pregnant women last season.

Included in the analysis were 6225 women with data about seasonal influenza vaccination who gave birth between September 1, 2009, and March 12, 2010, and 5112 women with data about H1N1 vaccination who gave birth between October 1, 2009, and March 12, 2010.

Among the 10 states, seasonal influenza vaccination rates ranged from 36.6% to 68.3% (median, 50.7%). H1N1 vaccination rates ranged from 26.9% to 72.4% (median, 46.6%).

To compare seasonal and H1N1 vaccination coverage with the same sample, the CDC analyzed data on 5052 women with live births between October 1, 2009, and March 12, 2010, for whom complete influenza vaccination data was available.

Overall, two thirds (66.0%) of these women received at least 1 vaccine, 34.1% received both vaccines, 19.7% received only the seasonal flu vaccine, and 12.2% received only the H1N1 vaccine.

Provider Recommendation Key

According to CDC, "large percentages" of women said their healthcare provider offered or recommended the seasonal influenza vaccine (67.4%) and the H1N1 vaccine (75.2%). These women were far more likely to get the seasonal flu vaccine than women who did not get this offer or recommendation (65.8% vs 19.6%; relative risk [RR], 3.3; 95% CI, 2.9 - 3.9).

The same was true for the H1N1 vaccine (60.1% of women offered or recommended it got it vs 5.9% of women who did not receive this advice; RR, 10.1; 95% CI, 7.7 - 14.3).

These findings reinforce previous findings that a healthcare provider's recommendation to get vaccinated is "key in vaccination acceptance," the CDC writes in the report. With the novel 2009 H1N1 virus, "the role of health care providers in reassuring pregnant women might have been critical because of patient concerns regarding the new vaccine," they note.

Continued Education Needed

Despite the greater uptake of influenza vaccine among pregnant women, "continued efforts to educate the public and health care providers will be needed to increase influenza vaccination coverage among pregnant women during the 2010-2011 season," the CDC emphasizes.

Among 2994 pregnant women who did not receive the seasonal influenza vaccine, 47.7% cited safety concerns for their unborn baby and 45.2% cited safety concerns for themselves; 72.1% said they typically do not get the flu shot.

Among 2602 who did not receive the H1N1 vaccine, 63.6% cited safety concerns for the baby and 61.4% cited safety concerns for themselves.

The researchers have disclosed no relevant financial relationships.

Morb Mortal Mkly Rep. 2010;59:1541-1545.

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