CDC urges workers to receive flu vaccine
Community outbreaks can threaten patients’ lives
With influenza season imminent, the federal Centers for Disease Control and Prevention urges health care providers to comply with vaccination recommendations, or face the very real possibility of threatening the lives of patients whose immunocompromised status renders them unable to fight off infection.
The CDC’s Advisory Committee for Immunization Practices (ACIP) recommends that hospital personnel be immunized against influenza,1 and at this time of year most hospital employee health practitioners are implementing immunization programs. Yet, despite annual vaccination admonitions, substantial proportions of health care workers manage to avoid the needle.
This behavior can have tragic consequences, says Nancy Arden, MN, epidemiologist in the CDC’s influenza epidemiology section.
"Achieving high rates of vaccination among health care providers, especially those who have frequent contact with high-risk patients and most hospital workers would be in that category can be very important, particularly when providers are working with immunosuppressed patients," Arden says. "However, there still is a certain percentage of physicians and nurses who think influenza is not a very serious illness, and they truly don’t understand why it’s necessary for them to protect their patients."
In an average year, influenza is associated with about 20,000 deaths. Some infections progress to pneumonia, and influenza can exacerbate other chronic conditions such as heart and lung disease. Rates of heart failure deaths increase during certain flu epidemics, Arden notes. Active hospital immunization campaigns should take place in the fall through November, she adds, but vaccine must remain available after that because "some [workers] don’t think about taking it until they start hearing about outbreaks."
Outbreaks are not uncommon in hospitals, Arden says, and can have particularly severe consequences in specialty units such as intensive care and pediatrics.
Unvaccinated HCWs can unintentionally trigger nosocomial outbreaks by transmitting infections acquired in the community. Workers can begin shedding virus before they experience symptoms. In addition, some HCWs will remain on the job even when they know they’re ill, "either because of their dedication or because they just don’t feel that they want to stay off work very long," she says. "Physicians are the worst, but nurses are pretty bad, too, about coming to work when they’re sick."
Accessibility boosts compliance
Even when workers stay home with their illness, they’re creating a problem for other HCWs who must cope with fewer staff and more patients in the midst of community outbreaks, Arden says. The only solution is widespread compliance with immunization programs.
Nevertheless, compliance in past years has been unimpressive. (See related stories in Hospital Employee Health, October 1995, pp. 128-130; October 1994, pp. 134-136.) An unpublished CDC survey found that 48% of 849 hospitals reported less than 25% of HCWS were immunized against influenza, while only 5% of hospitals said that more than 75% of workers were vaccinated. Another survey of 351 hospital employees and 55 hospital-based physicians revealed that 31% of employees and 57% of physicians complied with influenza vaccination programs in 1993-94.2
Several factors have been associated with increasing compliance, Arden says. One is providing vaccination at no charge to workers. Another is making vaccine easily accessible to workers on all shifts. A third is bringing vaccination to workers at job sites instead of requiring them to come to the employee health department. The latter can be accomplished by means of a mobile "flu cart" that makes scheduled rounds of hospital units and floors. (See related stories in Hospital Employee Health, October 1994, pp. 136-137; October 1993, pp. 133-136.)
During the 1995-96 flu season, the impact of influenza was more severe than during the previous season, but Arden discourages EHPs from attempting to boost vaccination compliance by issuing dire warnings about possible severe flu epidemics. Such predictions are difficult to make.
"It’s tempting sometimes to try to encourage people to get vaccinated by predicting an unusually severe season, but it’s not a good long-term policy," she says. "If we could do it, that would be one thing, but it’s really difficult. The best thing we can do is encourage people to be vaccinated every single year to keep up with the changes in the [influenza] strains."
Based on the CDC’s worldwide surveillance, all three influenza strains are expected this season. Last year, type A strains predominated, and "we saw very little of the influenza type B," Arden notes. "We expect to see more of influenza B this season because we saw an increase toward the end of last season, and that’s often a clue."
The trivalent influenza vaccine is manufactured to include all three circulating strains in a particular season. When there is a good match between vaccine and circulating viruses, influenza vaccine has been shown to prevent illness in approximately 70% of healthy people less than 65 years old.1 The strains to be included in each year’s vaccine are chosen based on surveillance of strains causing outbreaks in Southern hemisphere countries.
Virus strains expected this year are A/Texas/ 36/91-like (H1N1), A/Wuhan/359/95-like (H3N2), and B/Beijing/184/93-like. Arden says EHPs and other health care providers should not be confused if they notice that this year’s vaccine product includes two strains with different names. For the Wuhan component, U.S. manufacturers used a strain named A/Nanchang/933/95, and for the B component, the B/Harbin/07/94 strain was used.
"Those strains were chosen because they’re antigenically equivalent to the reference strains Wuhan and Beijing; they are virtually identical viruses," Arden says. "The reason they are used in the vaccine is because they grow better, which makes it easier to manufacture all the doses that are being made these days. We want to make sure people don’t think they’re getting the wrong vaccine."
The H3N2 strain is most often responsible for the highest mortality in outbreaks among all age groups, while the H1N1 strain mainly causes illness in children and younger adults. Arden says although both strains are expected to circulate this season, attempting to predict to what extent and in what regions of the country is fruitless.
"Some seasons we see outbreaks in various geographic regions all at the same time with the same strain; sometimes we see different strains predominating at different times during the season or peak activity at different times throughout the country, but there is absolutely no pattern to it whatsoever," she says. "Because influenza is so unpredictable, people need to be prepared for whatever strains circulate whenever they circulate. That’s a good reason for taking the trivalent vaccine every year."
[Editor’s note: Influenza surveillance information is available through the CDC Voice Information System (influenza update) at (404) 332-4551. Information is updated at least every other week from October through May. Updates are published weekly in the Mortality and Morbidity Weekly Report. Information regarding local influenza activity also is available through state or local health departments.]
References
1. Centers for Disease Control and Prevention. Prevention and control of influenza: Recommendations of the Advisory Committee on Immunization Practices. MMWR 1996; 45(No. RR-5).
2. Bratcher DF, Stover BH, Lane NE, et al. Compliance with national recommendations for TB screening/immunization of health care workers: Report from a children’s hospital. Presented at the 22nd annual conference of the Association for Professionals in Infection Control and Epidemiology, Poster #120. Las Vegas;1995.
3. Centers for Disease Control and Prevention. Update: Influenza activity United States and worldwide, 1995-96 season, and composition of the 1996-97 influenza vaccine. MMWR 1996; 45:326-329.
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