Pertussis boosters on tap for HCWs?

Immunity wanes in a few years

Pertussis outbreaks have continued despite a push to provide booster vaccines for adolescents and adults. The Centers for Disease Control and Prevention is now considering whether additional boosters may be needed, including for health care workers.

In 2012, there were more than 41,000 reported cases of pertussis and 18 pertussis-related deaths in the United States, mostly among infants younger than 3 months. Every state except California saw an increase in pertussis cases. (California had an outbreak that peaked in 2010 and continued into 2011.)1

Because of underreporting, the burden of pertussis is likely much greater than reflected in those numbers, Thomas Clark, MD, MPH, medical epidemiologist told the Advisory Committee for Immunization Practices (ACIP), a federal advisory panel. “We expect the resurgence of pertussis to continue,” he says.

One major problem: Immunity begins to wane just a few years after immunization with the acellular vaccine. In 2012, there was a resurgence of disease even among older children. Children receive the last of five diphtheria, tetanus and pertussis (DTaP) doses between the ages of 4 and 6. Last year, there was a spike in cases among children ages 10, 13 and 14.

“The switch to acellular vaccine may have changed the epidemiology of the disease,” Clark says.

In 1997, CDC recommended only acellular vaccines for the five-dose series because of safety concerns with the whole-cell vaccine. Now, there is new consideration of “priming” infants with one dose of the whole-cell vaccine.2

Meanwhile, in June, ACIP may consider recommendations for additional booster doses of Tdap, the adult acellular vaccine. They could add a single booster for older adolescents or young adults, or boosters every 10 years.

ACIP also could consider a different recommendation for health care workers, although Clark notes that “we don’t have evidence that health care workers are important in the spread of pertussis. Most babies get pertussis in their homes.” CDC currently recommends a single booster of Tdap for health care workers.

CDC is unlikely to change the post-exposure recommendations for health care workers, says Clark. CDC recommends post-exposure prophylactic antibiotics for all health care workers (vaccinated or unvaccinated) who could have contact with high-risk groups, such as infants and pregnant women. Other exposed health care workers should either receive prophylaxis or should be monitored for 21 days for signs and symptoms of pertussis.3

“There’s an indication that post-exposure prophylaxis does have a benefit [in preventing disease],” says Clark.

Yet vaccination continues to be the more important infection control measure, he says. “[Post-exposure prophylaxis] can protect individuals, but there’s not any evidence it can stop an outbreak,” he says.

References

1. Liko J, Robison SG, and Cieslak PR. Letter: Priming with whole-cell versus acellular pertussis vaccine. New Eng Jrl Med 2013; 368:581-582.

2. Centers for Disease Control and Prevention. Immunization of healthcare personnel: Recommendations of the Advisory Committee on Immunization Practices. MMWR 2011; 60:1-45