CDC updates flu vaccination recommendations

Aug 18, 2011 (CIDRAP News) – With shipments of influenza vaccine for the upcoming season arriving at healthcare providers' offices, the US Centers for Disease Control and Prevention (CDC) today released its advisory group's latest recommendations, which have a few changes that apply mainly to younger children and people who have egg allergies.

Also, with a look back at the past flu season, the CDC released its latest findings about uptake of the vaccine in healthcare workers and pregnant women, two groups that it has focused on in its efforts to boost vaccine coverage.

Carolyn Bridges, MD, associate director for adult immunization with the CDC's National Center for Immunization and Respiratory Disease, told reporters at a media briefing today that there is plenty of vaccine available for healthcare providers to get an early fall start on flu vaccination.

Vaccine companies have projected that they expect to make a record number of doses for the US market this season, between 166 million and 173 million. This year's vaccine targets the same three strains as last year, including the 2009 H1N1 strain. The US Food and Drug Administration (FDA) said in an Aug 17 update that it has so far released 272 lots of flu vaccine for distribution, up from 119 as of Aug 3. The total includes vaccine from all six pharmaceutical companies that are making vaccine for the 2011-12 US flu season.

Last year was the first year of a universal flu vaccination recommendation in the United States, with the CDC callig for immunization for everyone except babies under 6 months old. Annual flu vaccine campaigns can be tricky, because antigen growth can be unpredictable for vaccine producers hoping to match shipments with time of highest demand in the fall.

The US and other nations promote the flu vaccine as the principal strategy to reduce the annual burden of the disease, especially in groups at high risk for complications, such as those with underlying medical conditions. Health officials also depend on annual demand for the vaccine to keep the manufacturing capacity robust in case a pandemic strain arises.

However, the effectiveness of flu vaccines is well below that of many other immunizations, such as measles. The CDC says that inactivated flu vaccine can be 70% to 90% effective in preventing flu in healthy, nonelderly adults when the vaccine and circulating viruses are well-matched. But studies have shown that the effectiveness can be significantly lower in people older than 65 and in seasons when the vaccine doesn't match up well with the circulating viruses.

Bridges said this year's flu vaccine recommendations from the CDC's Advisory Committee on Advisory Practices (ACIP), published today in an online edition of Morbidity and Mortality Weekly Report (MMWR), are shorter than for past seasons, because the same three flu strains from last season are included in the 2011-12 vaccine and the nation is entering its second season with its universal recommendation.

Even though this year's vaccine contains the same three strains as last year's, the CDC is advising annual vaccination for most Americans. "Levels of protective antibodies can decrease, especially in the elderly and people who have compromised immune systems," she said, adding that annual vaccination can ensure optimal protection.

A change in advice on young children
One change in this year's recommendations, though, touches on the repeat appearance of the same three strains in the vaccine. In past years, ACIP has recommended that children aged 6 months to 8 years who received only one dose the previous season should receive two doses the following season. However, because the vaccine strains haven't changed this year, children in this age-group who received only one dose last season need only one more dose this season.

The recommendation could change for the 2012-13 season if the mix of strains in the flu vaccine is different, the CDC noted. It said the two-dose recommendation remains in place for children who didn't receive the vaccine last year or for whom vaccination status is unknown.

Also new to the annual flu recommendations is more in-depth guidance about flu vaccination for people who have egg allergies. Bridges said new research findings have suggested that vaccination is safe for most people with egg allergies, and the guidance reflects the new information.

Medical authorities have long urged caution regarding flu shots for those with egg allergies because of the concern that residual egg protein in the vaccines, which are grown in eggs, might cause a reaction.

Patients who have experienced only hives after exposure to eggs should receive the vaccine only from providers who can identify possible reactions, and people who have had more serious reactions from eggs, such as respiratory distress, should consult with a physician with allergy expertise before receiving the vaccine, the CDC advises.

The new ACIP recommendations mention two of the newest flu vaccines made by Sanofi, an intradermal trivalent inactivated vaccine (TIV) indicated for people ages 18 to 64 and a high-dose TIV indicated for people age 65 or older. The panel did not indicate a preference for the new alternatives over other TIV preparations.

Coverage in healthcare workers
In new reports on flu vaccine uptake during the 2010-11 season, the CDC said coverage in healthcare workers improved slightly and coverage for pregnant women held steady at a level reached during the 2009-10 pandemic months. Both studies involved Internet panels.

The survey of healthcare workers was conducted in April and included three online survey panels totaling 1,931 participants. Of the group, 63.5% reported that they received the flu vaccine during the 2010-11 season, an increase from 61.9% reported the previous season. Workers who had direct contact with patients, such as physicians and nurse practitioners, were more likely to be vaccinated.

Uptake was high (98.1%) in facilities that had mandatory flu vaccine requirements. Those who weren't required to receive the vaccine reported they were more likely to be immunized if it was offered free on site and for an extended length of time.

For pregnant women, uptake was 49%, nearly the same as the 50% level set during the 2009 pandemic, the CDC reported. The survey was conducted in April among 1,457 respondents who were pregnant at any time between October 2010 and January 2011. The CDC noted that the level is still below the 80% Healthy People 2010 target for this group.

The study revealed that women who were advised by a healthcare provider to be immunized were five times more likely to receive the vaccine. Four in 10 said their providers did not offer them the flu vaccine.

More efforts are needed to encourage providers to offer the vaccine to their pregnant patients, and more work is needed to remove barriers, such as lack of training or vaccine storage equipment, that make it difficult for clinics to offer it as part of routine practice, the CDC experts noted.

CDC. Prevention and control of influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices (ACIP), 2011. MMWR 2011 Aug 18;60(early release):1-6[Full text]

CDC. Influenza vaccination coverage among health-care personnel—United States, 2010-11 influenza season. MMWR 2011 Aug 19;60(32):1073-77 [Full text]

CDC. Influenza vaccination coverage among pregnant women—United States, 2010-11 influenza season. MMWR 2011 Aug 19;60(32):1078-82 [Full text]

See also:

Aug 17 FDA flu vaccine lot release status

CDC information on flu vaccine effectiveness

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