"Cocooning" is Goal to Protect Very Young, Elderly From Contracting Pertussis

Although the incidence of pertussis has lessened considerably since the 1920s and 1930s—when as high as 150,000 cases and 9,000 deaths annually were reported to the Centers for Disease Control and Prevention (CDC)—it remains a significant threat to some segments of the population. Babies less than 6 months old who have yet to receive their complete primary vaccine series and the elderly are particularly susceptible to serious illness and death from pertussis. The recent outbreak in California involving more than 6,600 confirmed cases and 10 infant deaths (as of November 9) illustrates the continuing health risks of this infectious disease.

“It is typical for pertussis to cycle, which means we have more cases every four to five years. The last upsurge occurred in 2004-2005, so the increased cases we are seeing now are consistent with the disease’s cyclic nature,” says Alexis Elward, MD, infectious diseases attending physician and medical director of infection control at St. Louis Children’s Hospital. “The pertussis cases in California, however, are well beyond anything seen in many years.”

A contributing factor to the spread of pertussis is that the protection given by the initial vaccine series given during infancy wanes over time, leaving school-aged children and adults vulnerable to infection. “There’s a second peak in terms of age of diagnosis in 11- to 20- year-olds. Typically these older children and teens with pertussis do not develop life-threatening complications as do infants and the elderly,” says Dr. Elward. “However, people this age as well as adults who have not been revaccinated become reservoirs for transmitting pertussis to infants and young children.”

Various studies have shown that household members are responsible for 75 percent of pertussis transmission to infants. Parents represented more than half of the source cases and mothers were the source in more than one-third of cases.1,2,3

These types of findings have led the CDC’s Advisory Committee on Immunization Practices (ACIP) and infectious diseases specialists throughout the country to advocate regular pertussis revaccination for older children and adults.

“In effect, people of all ages undergoing revaccination for pertussis would create a ‘cocoon’ of protection for vulnerable infants and the elderly,” says Dr. Elward. “This is especially important for anyone having contact with these populations; for instance, teenagers who do babysitting, health care workers caring for the young or old, and parents and grandparents.”

Tdap (tetanus, diphtheria, pertussis) vaccine was licensed for use in people aged 11-64 in 2005. In October 2010, the ACIP expanded its recommendation to include adults over 65 and children aged 7-10 who are unvaccinated or who did not receive a complete primary series of the DTaP vaccine when they were younger.

“The ACIP also recommends administering the Tdap vaccine no matter how long ago a person has received other tetanus-containing vaccines,” says Dr. Elward. “There’s been no evidence that adverse events occur if you administer two tetanus-containing vaccines close together.”

In the midst of its pertussis outbreak, California is going a step further by giving the Tdap vaccine to pregnant women. Current CDC recommendations are that pertussis vaccination be considered during pregnancy if the benefit outweighs the risk. “Vaccination during pregnancy has several advantages “says Dr. Elward. “In addition to the mother being protected against disease during pregnancy and after birth, another potential advantage is that the mother’s antibody could cross the placenta during the third trimester, helping to give her baby some immunity.” Locally, current practice has been to vaccinate women in the immediate post-partum period. Household contacts and caregivers of infants should also receive vaccination.

Sources:
Wendelboe AM, Njamkepo E, Bourillon A, et al. Transmission of Bordetella pertussis to young infants. Pediatric infectious Disease Journal. 2007;26:293-199.
Bisgard KM, Pascual FB, Ehresmann KR, et al. Infant pertussis: who was the source? Pediatric infectious Disease Journal. 2004;23:985-989.
Gerbie MV, Tan TQ. Pertussis disease in new mothers: effect on young infants and strategies for prevention. Obstetrics and Gynecology. 2009;113 (2 Pt 1):399-401.
 
Pertussis Symptoms, Diagnosis and Treatment
Pertussis usually takes one to three weeks to incubate, with patients typically passing through three stages. The most common symptoms are:

Catarrhal stage (often lasts one to two weeks)

• mild cough
• low-grade fever
• runny nose

Acute phase (may last for several weeks)

• cough gets worse and comes in severe fits
• cough is dry and harsh
• cough ends with a whoop sound on inspiration
• child may vomit with the coughing and appear to be strangling
• cough can be started by various factors, including feeding, crying or playing
• pneumonia may develop

Recovery phase (usually begins around the fourth week)

• vomiting and whooping cough cease first
• cough usually decreases around the sixth week but may continue on occasion for the next one to two months

“When a pediatric or adult patient has a cough that lingers for more than a week, pertussis should be added to the differential diagnosis,” says Alexis Elward, MD, infectious diseases attending physician and medical director of infection control at St. Louis Children’s Hospital. “Pertussis in its early stages is difficult to diagnose because its symptoms resemble those of a cold or influenza. If there is a suspicion of pertussis, a polymerase chain reaction (PCR) test is the best way to diagnose it. This should be done as soon as possible so that the patients and their family members can be started on azythromycin once the diagnosis is confirmed.”

Azythromycin works to decrease the burden of infectious organisms in patients, which helps lessen transmission of pertussis. However, it does not alter the course of the disease for individual patients.

“The pertussis bacteria makes a chemical that’s a toxin, and that is what causes the symptoms,” says Dr. Elward. “Patients don’t start to get well until their bodies can clear the infection away.”

For patients who become seriously ill—most often young babies—hospitalization to provide supportive care like intravenous fluids and total parenteral nutrition is needed.

“These babies can develop apnea and bradycardia, and it is heartbreaking to see them struggle for breath and cough until they are blue in the face. The disease can be hard on their growth and development because they don’t want to eat and vomit after a long paroxysm of coughing,” says Dr. Elward. “With the Tdap vaccine now available for adolescents and adults, it is imperative that we all work to ensure widespread vaccination against pertussis so that we can protect the most vulnerable within our population.”