Updates

by Carol A. Kemper, MD, FACP

Flu Shortage—Who Cares?

Isn’t it amazing how people don’t want something until they cannot have it. This year’s nationwide shortage of flu vaccine, caused by manufacturing problems at the Chiron facility in England, has generated more bellyaching, finger pointing, and outright panic than is justified—it makes one almost wonder if the shortage was just an attempt to get people to want the flu shot. Let’s put this in perspective. Every year, hundreds of thousands of doses of flu vaccine go unused and are destroyed, as the Public Health Service and healthcare providers urge patients to get vaccinated. At best, ~65% of the elderly and at risk patients receive the flu vaccine. Last year, when flu vaccine was offered free of charge to patients in our hospital, about 30% refused.

People need to understand some basic information about the flu shot: vaccination against the flu offers only partial (~70%) and temporary protection against a few flu viruses. In contrast, the natural immunity one develops from actual infection is much broader and more durable, lasting an estimated 3 to 5 years following infection. Every year, influenza experts meet to determine the composition of the following year’s influenza vaccine, which amounts to little more than a crapshoot. The vaccine usually contains 3 strains of virus: 2 type A strains and 1 type B strain. For the 2003-2004 flu season, the trivalent influenza vaccine included A/Panama/2007/99 (H3N2)-like antigen, A/New Caledonia/20/99(H1N1)-like antigen, and B/Hong Kong/330/2001-like antigen. Last year, it was estimated that only 10-14% of those who received the flu vaccine were protected against the strain of flu they were exposed to. This year’s vaccine is identical.

I’ve overheard perfectly healthy 30-year olds complaining they cannot get vaccine—although they look puzzled when you ask them if they’ve ever received one before. One mother was furious that her 4-year-old was denied a vaccine by her pediatrician—until I pointed out to her that that was a good thing; it meant her child was healthy and not at high risk for complications of the flu. Interestingly, the mother desperately explained the child really need the vaccine because she’d had the flu last year—and did not understand the child probably already had much better immunity than any vaccine could provide.

Most likely, there will be enough vaccine for those high-risk patients who may benefit the most from vaccination. The print and mogul media have a responsibility to quell peoples’ fears of epidemics and shortages, provide the public with accurate information about the flu shot, and encourage healthy people to pass on vaccination.

Can Cutaneous Zoster Result in Airborne Transmission?

Source: Suzuki K, et al. Clin Infect Dis. 2004:189:1009-1012.

A frequent question, when a patient with localized cutaneous zoster is admitted to hospital, is the appropriate infection control precautions. Are standard and contact precautions sufficient? Which immunosuppressed patient requires respiratory isolation? Do patients with AIDS and zoster require respiratory isolation? And, can a floor nurse make this assessment?

Using a highly sensitive PCR, Suzuki and colleagues assessed the presence of VZV DNA in swab specimens from cutaneous dressings, throat swabs, and from air purifiers in 13 patients hospitalized with cutaneous zoster, who were placed in respiratory isolation with air purifiers. Nine of the patients had moderate cutaneous involvement, and one had severe disease with extensive dermatomal involvement. At least 4 of the patients were considered immunosuppressed, 2 of whom were receiving steroids. All of the patients received parenterally administered acyclovir, beginning anywhere from day 1 to day 5 of hospitalization.

Patients were randomly assigned to conventional gauze bandages or a hydrocolloid dressing (Duoactive, Bristol Meyer Squibb). Specimens were obtained every day between day 4 and day 7 of their outbreak. In the gauze group, VZV DNA was detected in 22 of 23 samples taken from the surface of dressings, in throat specimens of 4 patients (11 of 23 specimens), and in the air filters from all 6 patient rooms (13 of 23 samples). Interestingly, air filter specimens were positive in 2 of the patients with negative throat swabs. In contrast, in patients whose lesions were covered with hydrocolloid dressing, none of the specimens from dressings or the air filters were positive, although 2 patients had positive throat swabs.

These data suggest that even localized cutaneous zoster, in immune competent hosts, can result in airborne spread of virus, although whether the viral particles detected by these molecular means is sufficiently viable to cause infection, is not known. Hydrocolloid dressings appear much more effective than standard gauze dressings in preventing passage of viral DNA particles through dressings, and may reduce the risk of airborne spread of virus.

If It Was a Bear. . . Part II

ProMED-mail post November 5 and November 8, 2004; www.promedmail.org

Last month, it was postulated in this column that brown bears, which rarely attack people, are less likely to harbor oral anaerobes than their meat-eating counterparts, possibly because their diet consists mainly of berries, grasses, and seeds.

Anaerobes aside—authorities in central Romania have declared a rabies alert, and sealed off a forested area, following a brown bear that savaged 11 people in the area. Several people were just out foraging in the woods that day, one of whom was gathering mushrooms. Seven people were severely injured, and one has died. The bear was shot and killed by hunters several hours following the attack, and tests confirmed the bear had rabies the next day. A total of 97 persons who had contact with the victims have been vaccinated and/or received immune globulin. The area is currently sealed off for 15 km around the radius of the attack, with a 3rd degree quarantine—meaning that all animals in the zone are being monitored and vaccinated for rabies—including oral vaccine for all foxes.

Breakthrough Fungal Infection With Voriconazole

Source: Imhof A, et al. Clin Infect Dis. 2004;39:743-744.

Over the years, we’ve seen sequentially more resistant breakthrough fungal infections in immunosuppressed patients receiving prophylactic antifungal therapy. When fluconazole became available, the rate of breakthrough Aspergillus infection increased. With the increased use of itraconazole, and now voriconazole in immunosuppressed patients, we are just beginning to see an increase in azole-resistant yeasts and zygometes infection.

During a 5-year period, 13 of 139 patients (9%) who had undergone stem cell transplantation, who were receiving voriconazole at the Fred Hutchinson Cancer Research Center, developed breakthrough fungal infections. Four patients developed fungemia due to Candida glabrata resistant to voriconazole (MICs > 1 mcg/mL), 6 patients had zygomycetes, and 2 patients developed infection from either Aspergillus ustus or A. terreus. The patients were generally receiving voriconazole for suspected or documented Aspergillus infection, although a few were receiving it for primary prophylaxis. Caspofungin was used in combination with voriconazole in 2 of the patients, one of whom developed infection with both C. glabrata and rhizopus.

The emergence of voriconazole-resistant yeasts has been increasingly documented. Many of these infections tend to be C. glabrata, which has lower rates of response to salvage treatment with voriconazole. In addition, voriconazole has limited activity against the pathogenic zygomycetes. As more immunocompromised patients receive voriconazole, fewer infections due to Aspergillus are likely to occur, but the rate of breakthrough infection with some of the nastier zygomycetes, for which there is often little effective therapy, will increase.

Carol A. Kemper, MD, FACP, Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases; Santa Clara Valley Medical Center Section Editor, Updates Section Editor, HIV, is Contributing Editor for Infectious Disease Alert.