Should you get the live attenuated flu vaccine?

ACIP to present new guidelines

Moving to clear up the considerable confusion of the last flu season, the Centers for Disease Control and Prevention (CDC) has drafted new guidelines for health care workers who receive the live attenuated influenza vaccine (LAIV). The CDC’s Advisory Committee on Immunization Practices (ACIP) is expected to soon release new guidelines that will allow the LAIV nasal spray vaccine (FluMist, MedImmune Vaccines Inc., Gaithersburg, MD) to be used more liberally in health care settings with fewer restrictions on immunized workers.

Tom Tolbert, MD, MPH, an infectious disease physician at Vanderbilt University Medical Center in Nashville, TN, is the lead researcher of a recent study that directly resulted in the new CDC guidelines. The data from this study show health care workers who receive LAIV are unlikely to shed flu virus more than seven days after vaccination, meaning the previous 21-day furloughs are unnecessary.

"If you going to reduce the activities of health care workers, we think you could probably limit that to a week," he continues. "In the first few days after vaccination with live flu vaccine in adults, [shedding] is fairly [common]. Half of the adults in our study shed. But by one week after that, that number was markedly reduced, and we did not find any evidence of shedding after day seven.

"This is an attenuated virus. It is temperature-sensitive, and it is not supposed to replicate in the lower respiratory tract," Tolbert explains. "So in theory, if you were to transmit this virus, it should not cause disease. In actuality, you are almost secondarily vaccinating individuals. But the one caveat is that we don’t know if there is a chance that the attenuated virus could cause disease in an immunocompromised individual. There are people who think no’ and people who think yes.’"

In that regard, the new ACIP guidelines will stress that potential transmission from a recent vaccinee only poses a threat to the most severely immunocompromised patients.

Health care workers need influenza vaccine

While the ACIP guidelines remain to be finalized, the draft version, Jeff Stoddard, MD, MPH, senior director of MedImmune’s medical affairs influenza program, has seen emphasizes the importance of flu vaccination for health care workers, he says. "One thing that the new ACIP guidelines will say very clearly is that health care workers, first and foremost, need to be vaccinated against influenza," he notes. "That was a point that got lost in the all the confusion last year. A lot of conscientious health care workers were surprised by how much focus there was on what one shouldn’t do in terms of immunization as opposed to what one should do."

In general, ACIP recommendations will express no preference between the inactivated vaccine and LAIV for most health care workers treating most patients, Stoddard adds. Indeed, some see the arrival of the new vaccine as an opportunity to improve traditionally dismal levels of health care worker flu immunization. "I think everyone on all sides of this debate would agree that health care workers need to improve their rate of immunization," he says. "Influenza is a major of cause of nosocomial infections and morbidity and mortality in many high-risk populations. The fact that so many health care workers in this country forgo immunization against this preventable disease is really a national disgrace. It needs to be rectified," adds Stoddard.

Logistics difficult to manage

While few would dispute health care workers need to improve their rate of influenza immunization, William Schaffner, MD, chairman of the department of preventive medicine at Vanderbilt, finds a few devils in the details. For example, even if the furlough period can be reduced safely from 21 to seven days, the vaccine still presents logistical problems, he notes.

"I believe the furlough issue will continue to pose difficulties," Schaffner says. "We’re in circumstances where [agencies] are running on very tight budgets, and the notion of using a vaccine that will oblige [an agency] to give a worker seven days off — or even if they arrange it around a weekend or whatever the call schedule is — it will present difficulties. It is still much easier to use the injectable vaccine."

Home health facilities also must factor in that the mist vaccine is generally more expensive and the at-risk patient population remains somewhat nebulous, he explains. "I think we will have some [intense] discussions about what severely immunocompromised’ means," Schaffner adds.

"We will have to sort out who could or could not get the nasal spray vaccine based on that. Then there will be other clinicians who come forward with questions about other categories of immunocompromised patients — cancer patients at the nadir of their chemotherapy. Isn’t that comparable? There will be some HIV patients who are profoundly immunocompromised, and that question will come up. How can the ACIP distinguish between these patients?" he asks.

What about workers who receive LAIV from their own provider or visitors who have recently used the mist immunization? "I think asking health care workers to tell their supervisor if they receive the spray vaccine will continue to be requested," Schaffner notes. "I don’t know how much you can do about visitors [or family members] in any practical sense."

Schaffner maintains that the likelihood of any actual transmission of vaccine virus to a patient is "infinitely small." The issue may be as much about legal liability as infection control. "There remains the issue, which came up last year, about the distinction between the ACIP recommendations and what is stated in the package insert [the 21-day period]," he says. "For all of those reasons, plus cost, I believe that the injectable vaccine will continue to be the dominant vaccine used in the [health care] environment. A few years from now when more experience [with LAIV] has accumulated, and if there is no evidence of transmission, then everyone may be a bit more relaxed about its use," adds Schaffner.

A factor that gets somewhat lost within all the debate is that LAIV has not been primarily marketed to health care workers. "That has not necessarily been a targeted group," Stoddard says. "But certainly, we do feel that any vaccine that is licensed by the FDA to prevent influenza ought to be available to health care workers who are hoping to do the right thing and protect their patients."

Impact on children

Indeed, the needleless vaccine may have its greatest ultimate impact on children, a population the CDC is viewing with more concern regarding influenza. As of March 27, 2004, the agency had received reports of 142 influenza-associated deaths in U.S. residents age 18 and younger during the 2003-2004 season. There is accumulating evidence to suggest that immunizing greater numbers of children would not only protect the pediatric population but their adult high-risk contacts, Stoddard notes.

"Children over the age of 5 are on label [for LAIV]," he says. "We did our pivotal efficacy study in children down to 15 months, but we only got the label for kids over 5 years. That is because we need more data on the younger kids. We hope to have this vaccine licensed down to early infancy in the next couple of years."

While the vaccine holds much potential to reduce the toll of annual flu, the live virus moniker has become something of a lightning rod. "Unfortunately, there are a lot of misconceptions about live, attenuated vaccines," Stoddard says. "People forget that polio was eradicated primarily through the use of live attenuated vaccines. People forget that every day, pediatricians use four live attenuated vaccines in their patients: measles, mumps, rubella, and chickenpox."

And a couple of fairly staggering numbers may be lost in the minutiae as well: Every year, influenza hospitalizes 114,000 people and kills 36,000 in the United States. "It is important to understand that influenza is the No. 1 vaccine-preventable cause of death in this country," Stoddard points out. "It is one of the only communicable diseases that has not been brought under control despite having several tools in the armamentarium, including an inactivated vaccine."

Recommended reading

• Centers for Disease Control and Prevention. Advisory Committee on Immunization Practices. Using live, attenuated influenza vaccine for prevention and control of influenza. MMWR 2003; 52(RR13):1-8.