US data show higher flu vaccine uptake in kids, adults, health workers

Preparing a flu vaccine
Preparing a flu vaccine

Courtesy of the National Foundation for Infectious Diseases

The US Centers for Disease Control and Prevention's (CDC's) final flu vaccine coverage estimates for the 2012-13 season, released today, showed a healthy bump in children and a small gain in adults.

The CDC also found improved flu vaccine coverage in healthcare workers, one of the groups the agency has targeted with more intensive efforts to raise immunization levels.

Federal officials unveiled the findings today at a press conference sponsored by the National Foundation for Infectious Diseases (NFID) at the National Press Club in Washington, DC. The event was part of a broader effort to rally health groups and the public behind this season's flu vaccination efforts.

Vaccine makers expect to produce about 135 million doses for the US market, and so far 73 million doses have been distributed, according to the latest estimate from the CDC. Two new types of vaccine will debut this flu season, a quadrivalent (four-strain) version containing two influenza B strains offered by three different companies and a cell-based version, made by two companies, including Protein Sciences' FluBlok, which has been recommended for adults up to age 49 who have egg allergies.

Health officials said today that limited quantities of quadrivalent flu vaccine will be available in its first season, and that some people may not be able to find it in their area. According to an earlier report, roughly 25 million doses of the 135 million to 139 million doses manufacturers expect to produce will be the quadrivalent version.

Recent analyses of flu vaccines have found that efficacy averages about 60% in non-elderly adults, lower than health officials would like. However, there is broad agreement that current vaccines should be used until better, more effective ones are developed.

Though the flu season hasn't started in the United States, media reports are starting to pop up about outbreaks, including in the Los Angeles area and in South Carolina. Paul Biddinger, MD, medical director of Emergency Department Operations at Massachusetts General Hospital told reporters that his department has already treated a few patients who have been hospitalized with influenza infections.

Howard Koh, MD,MPH, assistant secretary for health at the Department of Health and Human Services (HHS), said it's impossible to predict what the upcoming flu season will be like, because influenza is wildly unpredictable. For example, he said the 2011-12 season was unusually mild and was followed by an earlier, longer, more severe 2012-13 season marked by lots of H3N2 activity. "Our message is simple," he said. "Don't hesitate, vaccinate."

Full implementation of the Affordable Care Act, with open enrollment set to begin on Oct 1, will emphasize preventive care and public health and is expected to remove cost as a barrier to immunization against flu and other preventable diseases for many Americans, he said.

Anne Schuchat, MD, director of the CDC's National Center for Immunization and Respiratory Diseases, said health officials are buoyed by new findings from surveys that show an uptick in overall flu vaccine coverage levels for the 2012-13 season, especially in children.

The new estimates are based on two phone-based surveys, the National Immunization Survey (NIS) and the Behavioral Risk Factor Surveillance System (BRFSS). The CDC posted the results yesterday on its Web site. Overall, 45% of the US population age 6 months and older were vaccinated last flu season.

The percentage for children through age 17 was 56.6%, an increase of 5.1 percentage points from the previous season. Coverage was highest for children ages 6 months to 23 months—at 76.9%—and declined by age. The coverage increases were significant for two age-groups: children age 5 to 12 years, who saw a 4.4-percentage-point rise, and those ages 13 to 17, a group that experienced an 8.8-percentage-point increase, according to the CDC.

Over the past few flu seasons, the CDC has seen racial discrepancies in children's flu vaccination patterns recede, and last season that trend continued. Though coverage for African-American, Hispanic, and American Indian/Alaska Native children held steady at the previous year's levels, the CDC's surveys found increases for white children, Asian, children, and those of mixed race.

For adults, flu vaccine coverage rose slightly to 41.5% last season, an increase of 2.7 percentage points from the previous year. The CDC noted that for both kids and adults, state-specific coverage varied widely. For example, Florida had 30.8% coverage for adults, compared with 53.4% in Rhode Island. "We have a lot of room for improvement all around, but we did do better," Schuchat said.

She said it's not clear why children's vaccination rates are so much higher than those of adults. Possible reasons could include more frequent healthcare visits for children, which likely provide more opportunities for vaccination, she said.

She also noted that adults were the last group to be included in the universal flu vaccination recommendation, so more time may be needed for the public health messages to have an effect. Health officials have also observed that parents often seem more willing to protect their children than themselves.

Based on the survey results, the CDC estimated that 139.8 million people were vaccinated for flu from July 2012 through May 2013, which it said is too high, because the number is higher than the 134.9 million doses that were distributed for the season. The agency noted that the flu vaccination status was based on self or parental reports and is subject to recall bias.

For its estimates of flu vaccine coverage in healthcare workers and pregnant women, the CDC based its findings on an Internet panel. Schuchat said participants didn't know in advance that they'd be asked about flu vaccination. The CDC published reports for both group today in Morbidity and Mortality Weekly Report (MMWR).

The number of healthcare workers who reported flu immunization rose to 72% for the 2012-13 season, up from 66.9% the previous year. The highest coverage rates were in physicians (92.3%), pharmacists (89.1%), nurse practitioners and physicians assistants (88.5%), and nurses (84.8%). Coverage was much lower, however, in nonclinical staff (64.8%).

Overall, flu vaccination coverage has increased in all healthcare settings except for long-term care facilities, which lag at 58.9%. At today's press conference, health officials said free flu vaccine offered on multiple days could be one measure to boost vaccination levels in nursing home staff.

In pregnant women, health officials saw a boost in flu immunization levels in the wake of the 2009 H1N1 pandemic, which hit this risk-group hard, but coverage seems to have stalled at around 50%, according to the CDC's latest estimate.

This year's survey found coverage in this demographic to be 50.5%. In the previous seasons it was 49% in 2010-11 and 47% in 2011-12. "However," today's MMWR report said, "these estimates are not directly comparable because the change in the definition of vaccination status for this most recent season."

This year's survey found, though, that women who received a healthcare provider recommendation and an offer to vaccinate had higher levels of coverage compared with those who didn't, even when women had a negative attitude about the efficacy or safety of the vaccine.

Among women who reported both a provider recommendation and an offer of vaccination, 70.5% received the vaccine, compared with 46.3% in women who received a recommendation but no offer of vaccine and 16.1% in women who received no recommendation.

CDC. Influenza vaccination coverage among health-care personnel—United States, 2012-13 influenza season. MMWR 2013 Sep 27;62(38):781-6 [Full text]

CDC. Influenza vaccination coverage among pregnant women—United States, 2012-13 influenza season. MMWR 2013 Sep 27;62(38):787-92 [Full text]

See also:

Sep 25 CDC final national and state influenza vaccination estimate for 2012-2013

Sep 25 CDC flu vaccine distribution update

Sep 26 NFID press release

Aug 5 CIDRAP News story "Quadrivalent flu vaccines coming; companies cite good demand"

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