VAIL, COLO. – It’s a question hospital infection control officers field from physicians and other health care personnel every time a pertussis exposure occurs: "I’ve been vaccinated, so why do I have to get a course of azithromycin for postexposure prophylaxis?"
The Advisory Committee on Immunization Practices (ACIP) based its updated recommendation for antibiotic postexposure prophylaxis on the findings of a randomized trial known as the Vanderbilt Study. The results, while nondefinitive, suggested that a policy of watchful waiting with daily symptom monitoring for 21 days post exposure may not be as effective as azithromycin postexposure prophylaxis in preventing pertussis infection, Dr. Ann-Christine Nyquist explained at a conference on pediatric infectious diseases sponsored by the Children’s Hospital Colorado.
The ACIP recommendation is for antibiotic prophylaxis for all pertussis-exposed health care workers likely to secondarily expose high-risk patients, such as neonates and pregnant women. Other vaccinated health care workers could receive either postexposure prophylaxis or 21 days of symptom monitoring with prompt antimicrobial therapy to be started should pertussis symptoms arise.
For Dr. Nyquist, the issue is a no-brainer. The vaccine is not 100% protective, the duration of protection is uncertain, and the adverse impact of a pertussis outbreak in a health care facility is enormous.
"When I put on my hospital epidemiologist hat and I think about pertussis in my hospital, it scares me to death. I would give everyone I was concerned about 5 days of azithromycin at $60 a pop," said Dr. Nyquist, professor of pediatrics at the University of Colorado, Denver.
The children’s hospital affiliated with Vanderbilt University, Nashville, Tenn., has a universal tetanus-diphtheria-acellular pertussis (Tdap) vaccine immunization policy for all health care personnel. So it was an ideal location for a randomized comparison of two strategies to prevent infection following pertussis exposure in vaccinated physicians, nurses, and other health care personnel.
Following a pertussis exposure, health care personnel were randomized to 5 days of azithromycin or 21 days of watchful waiting. A bona fide exposure typically involved face-to-face exposure within a few feet when the health care provider wasn’t wearing a mask, or ungloved contact with a patient’s secretions.
Although 1,091 health care personnel enrolled in the trial, during a 30-month period only 86 subjects were randomized, limiting the statistical power of the findings. The key result: Only 1 of 42 patients who received postexposure prophylaxis met the prespecified definition of pertussis, compared with 6 of 44 in the watchful waiting group.
However, pertussis infection was defined quite strictly as a positive culture or PCR, a twofold increase in anti–pertussis toxin titer, or a single anti–pertussis toxin titer of at least 94 enzyme-linked immunosorbent assay units per milliliter. In fact, not a single study participant developed symptomatic pertussis, and the investigators concluded that "it is likely that none of the health care personnel who met the predefined serologic or PCR for infection were truly infected with pertussis" (Clin. Infect. Dis. 2012;54:938-45).
Dr. Nyquist noted that the Centers for Disease Control and Prevention (CDC) has identified health care workers as being at the epicenter of numerous pertussis outbreaks in hospitals. Health care personnel have regular contact with infected patients, and as adults they have waning immunity. The cost per hospital outbreak was calculated by the CDC at $44,000-$75,000.
"But that figure doesn’t include the human pain and suffering, which I would multiply maybe times five," she added.
ACIP recommends that all health care personnel with direct patient contact in hospitals or ambulatory settings receive a single dose of Tdap. In addition, at its June meeting ACIP directed the Pertussis Vaccines Work Group to explore the possibility of giving a booster dose of Tdap to health care workers in order to beef up their protection.
Dr. Nyquist reported having no relevant financial relationships with any commercial interests.