But a few outbreaks of whooping cough, known medically as pertussis, have been reported around the country this year. By far the biggest is in California, where state health officials counted 3,076 confirmed and suspected cases through last Tuesday, a number seven times higher than the same period last year. Eight infants have died.
No one is known to have died in Southeastern Pennsylvania. But the potential danger to infants who have not yet developed immunity - the vaccine is given in a series of shots at months 2, 4, 6, and 15 to 18, with a booster at 4 to 6 years - prompted the state's announcement Monday.
Health researchers in recent years have discovered that pertussis is far more common than had been previously believed. Hundreds of thousands of Americans probably contract it every year, thinking they have a run-of-the-mill cough.
Babies, however, can become quite sick. About 25 or 30 infants in the United States die each year from pertussis, nearly all of them under 3 months old, said Paul A. Offit, chief of infectious diseases at Children's Hospital of Philadelphia.
While many infectious diseases, notably the flu, spread quickly among children who then infect adults in the household, Offit said, pertussis infection occurs differently: Older children and adults get infected, usually are never diagnosed, and then transmit the disease to infants.
No pertussis vaccine offers more than a decade or so of full protection, he said, which is why the Centers for Disease Control and Protection several years ago recommended a booster shot at ages 11 to 12. Philadelphia last year began requiring that booster for entry into sixth grade, but many other jurisdictions haven't.
More are likely to do so in the future, and Offit said he expected federal recommendations for voluntary adult booster shots as well.
For older children and adults, he said, "the goal of the vaccine is to keep infants and young children out of the hospital and out of the morgue."
A spokeswoman for the Pennsylvania Department of Health said Monday that most of the whooping cough reported this year had been among children 8 to 12 years of age.
The state recommended that the combination childhood vaccine, known as DTaP, be given to all children who had not received the full series of shots. DTaP combines diphtheria, tetanus, and pertussis vaccines.
It also urged that the adolescent-adult booster, known as Tdap, be given to anyone ages 10 to 64 who has not been fully immunized; women of childbearing age before or immediately after pregnancy; and people who have contact with pregnant women or infants too young to have received the full series of vaccinations; and all family members and caregivers of infants.
Pertussis is a highly communicable disease that can last for weeks and in children typically cause spasms of severe coughing, "whooping," and vomiting.
After an incubation that most often is seven to 10 days but can be much shorter or longer, the illness first shows up as a runny nose, sneezing, low-grade fever, and occasionally, a cough that is similar to that of a cold, according to a state health department advisory.
It usually is not diagnosed until a week or so later, after the cough gradually becomes more severe; difficulty breathing in after uncontrolled coughing can cause a telltale high-pitched whoop.
The symptoms often worsen for one to two weeks and then continue for several weeks before subsiding.
Pertussis can be treated with antibiotics.
The most common complication, and the cause of most deaths, is secondary bacterial pneumonia.
The rise in confirmed and probable cases of pertussis was most pronounced in Delaware County, where five were reported the first three months of the year, followed by 44 cases the next three months, and then 19 in July, and 12 so far in August.
Delaware County does not have its own health department; the state provides most public-health services there, including the pertussis clinics.
Health officials in some other suburban counties said pertussis vaccine would be available, along with other required childhood vaccines, at regular clinics posted on their websites.
The state scheduled free pertussis vaccine clinics on Wednesday from 9 to 11 a.m. at the Delaware County State Health Center, 151 W. Fifth St., Chester; and Monday from 3 to 7 p.m. at Penn State Brandywine Campus' commons/athletic building, 25 Yearsley Mill Rd. (Route 352, enter at Campus Drive traffic light), Media.
For information, call 1-877-PA-HEALTH (724-3258) or go to www.vaccinesforlife.com/
Contact staff writer Don Sapatkin at 215-854-2617 or email@example.com.