By Dr. Sadiq Al-Nakeeb –
Whooping cough (pertussis) is an acute, highly contagious upper respiratory infection that leads to episodes of violent coughing. The disease is named for the characteristic sound produced when affected individuals attempt to inhale; the whoop originates from the inflammation and swelling of the laryngeal structures (voice box) that vibrate when there is a rapid inflow of air during inspiration.
Whooping cough is caused by an infection with a bacterium known as Bordetella pertussis. The bacteria attach to the lining of the airways in the upper respiratory system and release toxins that lead to inflammation and swelling.
Most people acquire the bacteria by breathing in the bacteria that are present in droplets released when an infected person coughs or sneezes. Dr. Al-NaKeeb says, “The infection is very contagious and is often spread to infants by family members or caregivers, who may be in the early stages of infection and not realize that they are suffering from whooping cough.”
The infection gradually resolves over a period of weeks, but the coughing paroxysms can persist for several months. The most common complication and the cause of most whooping cough-related deaths is secondary bacterial pneumonia. Secondary bacterial pneumonia is bacterial pneumonia that follows another infection of the lung, be it viral or bacterial. Secondary pneumonia is caused by a different virus or bacterium than the original infection. Young infants are at highest risk for whooping cough and also for its associated complications, including secondary pneumonia. Other possible complications of whooping cough, particularly in infants less than 6 months of age, include seizures, encephalopathy (abnormal function of the brain due to decreased oxygen delivery to the brain caused by the episodes of coughing), reactive airway disease (asthma), dehydration, hearing loss, and malnutrition.
Data indicate that secondary pneumonia occurs in about one out of every 20 infants with whooping cough, and one out of 100 affected infants develop convulsions. Most deaths from whooping cough have occurred in children who have not been vaccinated or who are too young to have received the vaccine.
Whooping cough commonly affects infants and young children but can be prevented by immunization with pertussis vaccine. Pertussis vaccine is most commonly given in combination with the vaccines for diphtheria and tetanus.
(Pertussis is the “P” in the DTaP combination inoculation routinely given to children, and the “p” in the Tdap vaccine administered to adolescents and adults.) Dr. Al-NaKeeb says, “Since immunity from the pertussis vaccine wears off with time, many teenagers and adults get whooping cough if they don’t receive boosters. It is especially important for people who are routinely around infants to get the booster.”
For maximum protection against pertussis, children need five TdaP shots. The first three vaccinations are given at 2, 4, and 6 months of age. The fourth vaccination is given between 15 and 18 months of age, and a fifth is given when a child enters school, at 4-6 years of age. Preteens going to the doctor for their regular checkup at 11 or 12 years of age should get a dose of the Tdap booster, and adults who didn’t get Tdap as a preteen or teen should get one dose of Tdap. The easiest way for adults to ensure immunity is to get the Tdap vaccine instead of their next regular tetanus booster.
The vaccine has been deemed safe for pregnant women. To protect their infants, most pregnant women who were not previously vaccinated with Tdap should get one dose of Tdap during the late second trimester or third trimester of pregnancy. If not administered during pregnancy, women should get the vaccine postpartum before leaving the hospital or birthing center. Getting vaccinated with Tdap is especially important for mothers and families with new infants as well as all people caring for newborns. When a woman receives the Tdap vaccine during pregnancy, the antibodies she develops to the Bordetella pertussis bacterium are transferred to the infant, providing some additional protection to the infant before the baby can be fully vaccinated.
As mentioned above, although whooping cough is considered to be an illness of childhood, adults may also develop the disease even if they were vaccinated as children. Because immunity from the pertussis vaccine decreases over time but does not necessarily disappear, adults who do become infected may have retained a partial degree of immunity against the infection that results in a milder illness.
Whooping cough in adults is more common than usually appreciated, accounting for up to 7% of adult illnesses that cause coughing each year. According to Dr. Al-NaKeeb, “Infected adults are a reservoir (source) of infection for children, so it is particularly important that all family members and caregivers of young infants be properly vaccinated.”
For more information about the effectiveness and safety of the whooping cough vaccine, please visit www.cdc.gov.