UNNECESSARY PAIN: DPT shots are not always effective. (AFP)

Attention all teenagers and adults, and especially grandparents younger than 65. Chances are you are vulnerable to whooping cough, the disease known medically as pertussis ? the only vaccine-preventable illness still on the rise in some countries.

The immunity you developed from the series of shots you most likely received as an infant and child wore off in five or 10 years. A booster shot is periodically needed to restore it.

Chances are, too, if you do contract pertussis, you may not know you have it, mistaking it for a common cold accompanied by a prolonged cough. When pertussis strikes beyond early childhood, its classic symptom ? frequent spells of breath-robbing coughs that end in a “whoop” ? is often absent, especially if the person was once immunised.

Although you will probably recover from an attack even without a confirmed diagnosis or any treatment, you can still transmit it to infants and children who are unprotected or incompletely protected by pertussis vaccine. They can develop life-threatening infections as a result. You can also transmit the infection to other teenagers or adults whose immunity has worn off and not been replenished by a booster shot. Even those who contracted pertussis as children are not protected for life.

The newest and best-controlled study conducted in the US found that pertussis accounted for “only 0.7 per cent of illness with cough that lasts more than five days and 5.7 per cent of illness with cough that lasts more than 56 days”, but that still translates to one million vaccine-preventable illnesses in adults each year. The reported number of cases, believed to represent a fraction of the real incidence, has risen to more than 25,000 in 2004 from a low of 1,010 in 1976.

No doubt many people have heard or read about the many recent mini-epidemics of pertussis among high school and college students. The debilitating attacks that often rob students of school time and adults of work time and may risk the lives of exposed infants and children can be prevented by a single injection of the newest long-lasting vaccine for people beyond early childhood.

In December, the American Academy of Pediatrics recommended universal vaccination of adolescents with one of the two new vaccines specially for people previously fully immunised.

The new vaccines, known as Tdap, have a triple benefit, bolstering waning or expired protection against tetanus and diphtheria, as well as pertussis. The “ap” stands for acellular pertussis, the current form of the vaccine. It causes far fewer adverse reactions than the old whole-cell vaccine first given in the 1940s. Then, more than 200,000 cases were reported each year.

The two vaccines licensed by the Food and Drug Administration last year are Boostrix by GlaxoSmithKline, for use in children 10 to 18, and Adacel by Sanofi Pasteur, for ages 11 to 64. Studies have shown that these vaccines are highly protective as boosters. To maintain protection against diphtheria, tetanus and pertussis (DTP), the immunisation should be repeated every 10 years. The safety and effectiveness of the adult vaccine for elderly and pregnant patients has not been determined. Experts recommend that this triple booster vaccine replace the diphtheria-tetanus shot commonly used as a booster for adolescents and adults.

Of course, it is critically important for every child to complete the primary series of immunisations with four doses of the infant vaccine known as DTP. The first three doses are given four to eight weeks apart beginning at age six weeks to two months, with the fourth dose administered six to 12 months after the third, usually by 18 months.

Those children who complete this primary series before age four should receive a fifth booster dose before entering school, usually around age five or six. They may not need another booster until 15. Pertussis is caused by a small rod-shaped bacterium called Bordetella pertussis. Its main weapon is a toxin that paralyses the hairs that line the respiratory tract and causes the tract to become inflamed. These toxic effects interfere with a person’s ability to clear pulmonary secretions and result in intense and prolonged coughing episodes.

In a typical case of pertussis, after an incubation period of seven to 10 days, the infection starts with a runny nose, sneezing, low-grade fever and a mild cough, much like a common cold.

The cough gradually becomes more severe, and after a week or two develops into severe coughing spells with numerous rapid coughs. At the end there is a high-pitched whoop as the lungs struggle to refill with air. Hence the name whooping cough. The cough can be so violent that ribs break. Vomiting and exhaustion may follow coughing spells, which tend to occur at night.

Pertussis can result in serious complications, including pneumonia, middle-ear infection, dehydration, seizures and encephalopathy. Eighty per cent of pertussis-related deaths occur in infants younger than a year old. When a teenager or adult previously immunised contracts an infection, the characteristic coughing spells may not occur or may be too mild to be recognised as a symptom. In mild cases, the infection can spread to others who are vulnerable through droplets from coughs and sneezes in the first three weeks of symptoms.