A whooping cough vaccine first introduced in the 1990s does not provide long-lasting immunity, state health officials said Wednesday, and helps explain why Minnesota has recorded more than 4,300 cases this year -- the highest number since World War II.
"We have the intersection of a peak in pertussis that occurs every few years, along with a population that is not as strongly immune," said Dr. Ruth Lynfield, Minnesota's state epidemiologist. "The whole country is experiencing a resurgence."
As a result, Lynfield reiterated a Health Department alert that children and pregnant women be vaccinated to prevent the spread of the bacterium that causes whooping cough, formally known as pertussis.
In addition, she said, parents with children ages 4 to 6 and in middle school should ask their doctors whether they need booster shots for additional protection.
"Immunity from this vaccine is very effective, but it is not as long-lasting,'' Lynfield said. "Rather than lasting for many years, the immunity wanes. [But] the vaccine is absolutely still a great tool and parents should use it."
Whooping cough cases cycle up every two to five years naturally, which could account for an outbreak that has struck Minnesota and the nation this year. Minnesota typically records 200 to 1,500 cases a year.
The disease has not caused any deaths in Minnesota this year, but it can produce severe coughs in children.
The disease is spread through droplets coughed by infected people and often begins with cold-like symptoms. It usually can be treated effectively with antibiotics. Infants, however, may not cough and instead suffer episodes of sleep apnea and difficulty breathing.
Health Department figures released Wednesday show 58 cases serious enough to require hospitalization. That includes 24 infants and 13 patients over age 18. Six people over 50 also were given advanced care.
The A-cellular vaccine, first introduced in 1991, was designed to alleviate the high, painful fevers that children commonly experienced.
Over the years, though, health officials noticed that the vaccine's ability to stave off the sickness weakened sooner than they anticipated.
Last fall, a federal advisory committee began studying whether there should be uniform booster-shot guidelines.
Lynfield also urged parents to keep their children home if they show symptoms of the disease.
"Middle school children who are sick should stay home because they are likely to spread the pertussis quickly to younger children," she said.
Paul McEnroe • 612-673-1745