Driven by mandates, vaccination-or-mask policies, reporting requirements, and other factors, healthcare worker flu immunization rates have risen 15.5% since the 2010-2011 season, the CDC reports.1

Overall, 79% of respondents reported having received an influenza vaccination during the 2015-2016 season, an impressive increase over time but only a relatively incremental improvement from the 77% coverage estimate in the 2014-2015 season. Still, the overall push continues, overcoming resistance by critics who question mandates for a seasonal vaccine that has only a 59% efficacy historically.2

Further complicating the CDC’s annual message for immunization is that the live attenuated mist spray has been dropped this year for lack of efficacy, and last year’s overall flu shot effectiveness was undermined by a mismatch with the circulating A strain.

“As far as efficacy, it’s the best we have,” said Wilbur Chen, MD, of the University of Maryland School of Medicine’s Center for Vaccine Development. “A vaccine that is at least partially protective is better than no vaccination at all.”

Chen spoke at a recent press conference on seasonal flu immunization at the National Foundation for Infectious Diseases (NFID) in Washington, DC.

Some clinicians and patients were taken aback by the CDC decision to drop the live attenuated influenza vaccine (LAIV) nasal spray as a recommended flu vaccine for the 2016-2017 season in the U.S. Citing declining efficacy that essentially bottomed out last flu season, the CDC did not recommend LAIV this year, though it will still be available in Canada.

Of course, the effectiveness of any flu vaccine may vary from year to year due to the vagaries of antigenic “drift” and the more dramatic “shift” of circulating influenza virus. In that regard, last year’s vaccine had only a 41% efficacy against the predominate H1N1 influenza A strain and 55% against circulating B strains.3 Given the negative view of vaccines by some members of the public, and the historical challenge to reach high flu immunization rates in healthcare workers, speakers at the NFID were reluctant to get mired down in discussions about vaccine efficacy or the lack thereof.

“Flu is unpredictable,” Tom Frieden, MD, director of the CDC, said at the press conference. “We know there’ll be a season, but when it is and which vaccines — which flu strain predominates — only time will tell. The safest thing you can do is to get vaccinated. And this vaccine does match the flu strains we’ve seen so far, but it’s still too early to predict what the rest of the season will hold.”

The three-component vaccines this year contain the following strains:

  • A/California/7/2009 (H1N1)-pdm09-like virus,
  • A/Hong Kong/4801/2014 (H3N2)-like virus, and
  • B/Brisbane/60/2008-like virus (B/Victoria lineage).

Four component vaccines will include the three strains above, plus B/Phuket/3073/2013-like virus (B/Yamagata lineage).

Perhaps a more real-world measure of flu vaccine efficacy is reduced hospitalizations. The CDC estimates that some 200,000 people are hospitalized with flu infection annually in the U.S., and the number seems to be increasing as the population ages.4

“A 5% increase in the flu immunization rate nationally would prevent nearly 10,000 hospitalizations and about 800,000 illnesses,” Frieden said.

HCW Rates

To estimate influenza vaccination coverage for the 2015-2016 influenza season, the CDC conducted an internet panel survey of 2,258 healthcare workers. Hospitals led the way with a 91% immunization rate, while healthcare workers in ambulatory care had an 80% rate, and those in long-term care settings were only at a 69% vaccination level. (For more information, see related story in this issue.) In percentages by job description, flu vaccination was highest among physicians (96%) and lowest among assistants and aides (64%).

There are several factors driving the trend of increasing immunization over time. For example, the Centers for Medicare & Medicaid Services has added impetus for immunization by requiring acute care hospitals to collect influenza vaccination coverage data for workers and report rates to the CDC’s National Healthcare Safety Network. The biggest factor, however, appears to be mandated policies, as CDC reported that during the 2015-2016 influenza season, vaccination coverage was 96.5% among healthcare personnel working in settings where the shot was required.

However, overall only 38% of healthcare workers surveyed were required to be vaccinated against influenza. Hospital mandates were in place for 61% of respondents. By occupation, 51% of physicians and 50% of nurses reported that they were immunized under a mandate. However, only 22.5% of assistants and aides reported influenza vaccination requirements.

Still, in contrast to the past struggles to get healthcare workers immunized, the field was framed as a success story at press conference.

“For [hospitals], more than nine out of 10 got vaccinated,” Frieden said. “That’s a steady increase. I can remember just a few years ago when that was down around 60%. Now, 96% of doctors got vaccinated.”

Typically, mandated flu shot policies have a declination clause for those citing a medical or religious reason not to be vaccinated. According to a separate report5 by the CDC, 11 states permit medical exemptions for vaccination requirements, four states permit religious exemptions, and 10 states permit philosophical exemptions.

Healthcare settings vary on how they handle these requests for exemption, with some allowing those not vaccinated to continue working if they wear a surgical mask during patient care activities. This is based on the concern that healthcare workers with early-stage, asymptomatic flu infection may transmit the virus to vulnerable patients. However, the approach has been also criticized for inducing a kind of stigma that increases pressure on healthcare workers to be vaccinated. Colorado, New York, and Rhode Island require hospital healthcare workers to wear surgical masks during flu season if they have been exempted from or declined vaccination, the CDC reports.

California state law requires employees to be offered vaccines free of charge and to sign a declination form if they choose not to be vaccinated. However, each local health department has the authority to issue requirements that apply to facilities within their jurisdiction only, which include — in some cases — that unvaccinated workers wear masks for patient care, the state health department clarified in response to an inquiry by HEH.

“Facilities must comply with a local health officer’s order,” the department said in an email. “In addition, some hospitals, clinics, and health systems have independently adopted vaccinate or mask policies for the healthcare workers in their facilities.”

For example, the policy posted on the state health department website for Tuolumne County, CA, states: “HCWs who decline to receive a seasonal influenza vaccination will be required to wear a surgical mask while working in patient care areas during influenza season, between November 1 and March 31 each year. … In addition to protecting the wearer from transmitting the influenza virus, masking requirements have strongly and consistently raised vaccination rates among healthcare workers.”

Another approach, taken at the University of North Carolina (UNC) Medical Center in Chapel Hill, is that any employee with fever — immunized for flu or not — cannot report to work.

“Our upper respiratory policy is that any employee with a fever can’t come to work; they have to be out of work for 24 hours minimum and it could be several days,” says David Williams, RN, of UNC occupational health. “They have to be fever-free for 24 hours to come back to work.”

In addition, if healthcare workers have upper respiratory-type symptoms of runny nose or cough, they have to wear a mask to go into patient care areas, he tells HEH.

“If they have symptoms that cannot be contained by a mask, they have to stay out of work,” he adds. “That is our general policy that applies to those with and without flu vaccination.”

The CDC survey1 found that, in the absence of mandated policies, flu immunization rates were highest (83%) for those workers in settings where vaccination was encouraged and available at the worksite at no cost for at least one day.

In contrast, only 45% of healthcare workers were vaccinated at sites where flu shots were not required, encouraged, or offered on site. This type of environment was reported by 21% working in ambulatory care and 28% of healthcare workers in long-term care, the CDC reported.

There are various educational approaches to improve vaccination rates, many of which include busting the common myths that the vaccine is unsafe or actually causes flu.

‘Might be Dying’

Taking a different tack is Terri Rebmann, PhD, RN, CIC, FAPIC, professor of environmental and occupational health at Saint Louis (MO) University. At a recent talk in Nashville at the annual APIC conference, Rebmann cited her own severe flu infection as a cautionary tale, saying she tells healthcare workers to compare the possible mild side effects of the vaccine with a full-blown flu infection.

“I actually had the flu and I was like, ‘oh my gosh, I think I might be dying,’” Rebmann said. “I had it for 10 days. I got it the year the vaccine coverage was really poor because the strains didn’t match. It was awful, so I’ve become much more passionate when I talk about the side effects of the vaccine versus the actual symptoms of the flu.”

Whereas some people can feel like they almost have a mild viral illness for a brief time after the flu shot, flu symptoms can be “extreme” in terms of high fever, sore throat, and severe body- and headaches, she said.

Frieden told a similar story at the NFID press conference, saying a CDC staff member had a severe flu infection last year.

“A young, healthy woman thought she was going to die,” he said. “She was desperately ill, really scared, sicker than she’d been in her life. That was flu. Flu each year sends hundreds of thousands of people to the hospital. In a bad year, it kills up to 49,000 Americans, including the elderly, people with underlying conditions, and infants. Each year, we see 100 or more infants or children who die from flu. And when we’ve analyzed those infants, we’ve seen that about 90% didn’t get vaccinated.”


  1. CDC. Influenza Vaccination Coverage Among Health Care Personnel — United States, 2015-16 Influenza Season. MMWR 2016; 65(38):1026–1031.
  2. Osterholm MT, Kelley NS, Sommer A, et al. Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis. Lancet Infect Dis 2012; 12:36-44.
  3. CDC. Summary of the 2015-2016 Influenza Season. September 29, 2016:
  4. CDC. Seasonal Influenza-Associated Hospitalizations in the United States. May 26, 2016:
  5. CDC. Office of State, Tribal, Local and Territorial Support. Menu of State Hospital Influenza Vaccination Laws. 2015-2016: