LANSING - As Michigan continues to see a high level of reported pertussis (whooping cough) cases in 2009, extending a trend noticed in the second half of 2008, health officials are reminding parents and doctors of the importance of vaccinating children, teens, and adults against this serious disease.

"This disease continues to challenge us," said Michigan Department of Community Health (MDCH) Director Janet Olszewski. "But we have new tools and strategies to help us in our prevention efforts."

In 2005, new pertussis vaccines for adolescents and adults were licensed. Prior to that, pertussis vaccines were available only for children less than 7 years of age, which left teens and adults at risk because immunity against the disease can weaken and disappear over time.

In the first half of 2009, 281 pertussis cases were reported. That compares to 315 cases in 2008, two-thirds of which came in the second half of the year. In 2007 there were 292 pertussis cases reported in Michigan.

"Pertussis is a bacterial respiratory infection that can occur in all ages," said Dr. Greg Holzman, chief medical executive for MDCH. "Babies are most severely affected. They're the ones at greatest risk of a complicated case of the illness, often requiring hospitalization and sometimes resulting in death. That's why it is absolutely critical that children get all their vaccine doses on schedule to give them as much protection as possible. It's also important that family members of young babies get a pertussis vaccine booster so they are protected from illness, and don't pass the illness to infants."

Holzman noted a recent study published in the June issue of the journal Pediatrics which found that children of parents who refuse vaccines are 23 times more likely to get whooping cough compared to fully immunized children. 

Another study published on Oct. 11, 2006 in the Journal of the American Medical Association (JAMA) also documented an increased level of the disease among children whose parents opted not to have them vaccinated against pertussis.

Infants should receive four doses of pertussis vaccine by the time they are 18 months old, and a routine booster dose is recommended for children before starting kindergarten. Another booster dose is recommended for adolescents, ideally at 11-12 years of age, and because vaccine protection for tetanus, diphtheria, and pertussis can fade with time, adults should also get a booster dose.

A pertussis booster vaccine, known as Tdap, is now recommended for adolescents and adults; it boosts protection against tetanus, diphtheria, and pertussis. Pre-teens going to the doctor for their regular check-up at age 11 or 12 years should get a dose of Tdap. Adults who didn't get Tdap as a pre-teen or teen should get a dose, as should adults who are healthcare workers or who care for infants.

Centers for Disease Control and Prevention (CDC) data for the U.S. indicate that between 2000 and 2005 there were 140 known pertussis-related deaths, 90% of which occurred in infants less than 1 year of age. About half were likely the result of exposure to a household member who had pertussis or an illness that was probably pertussis.

Additional background on pertussis

Pertussis is a respiratory infection caused by bacteria that spread easily among persons in close contact, such as members of the same household. The illness starts as with cold-like symptoms of runny nose, sneezing, mild cough, and is at that point indistinguishable from many other upper respiratory illnesses. But a week or two later, the cough worsens, becoming a series of severe, intermittent coughing fits, which make it difficult for the patient to get a breath. Children especially may emit "whoop" noise as they finally catch a breath, which is where the illness gets its nickname of "whooping cough." The bouts of coughing may end in vomiting and often leave the patient exhausted. This phase of the illness can last several weeks, followed by several more weeks of illness where the cough gradually begins to decrease.

Pertussis is often not recognized until the patient has been ill for many weeks.

Nationally, reported cases of pertussis have been rising over the past 20 years. In 2004, 25,827 were reported, the most in any year since 1959. Almost as many cases were reported in 2005. Experts believe that many cases likely go undetected and unreported, and that some of the increasing trend may be explained by better recognition and reporting of the disease.

Treating patients and those persons in close contact to them with an appropriate antibiotic is important because it helps shorten how long they are contagious, and may help prevent complications, although it doesn't tend to help lessen the severity of the cough.