by Mary Elizabeth Dallas
April 24, 2012
Health officials in Washington State recently announced that confirmed cases of whooping cough have reached epidemic levels. From January 1 to April 6, 2012, 776 cases have been reported, compared to 101 cases during the same time period in 2011, according to the U.S. Centers for Disease Control and Prevention (CDC). As a result, Washington is on track to have the highest number of reported cases of whooping cough in decades.
“We’re very concerned about the continued rapid increase in reported cases,” says Secretary of Health Mary Selecky in a statement. “This disease can be very serious for young babies, who often get whooping cough from adults and other family members.”
Meanwhile, the number of people diagnosed with measles in the United States reached a 15-year high last year, according to a new CDC report. There were 222 cases of measles in the U.S. in 2011, more than triple the usual number of about 66 over the past decade.
Why do these outbreaks happen?
The cause is twofold: a decrease in immunization rates and a decrease in immunity over time.
When fewer people are immunized, disease rates go up. In 2002, researchers found that unvaccinated people in a highly vaccinated community were less likely to get measles than vaccinated people in a community with low vaccination rates. More information on this phenomenon known as herd immunity can be found here.
Despite the availability of a vaccine to prevent whooping cough, epidemics occur every three to five years, according to the CDC. Vaccines you get in childhood may not fully protect you when you are an adult. (Learn more here.)
“Many adults don’t realize they need to be vaccinated, or they assume they have been,” warns Washington State Health Officer Dr. Maxine Hayes.
But it’s not only adults who are losing their immunity. Data from a 2010 outbreak of whooping cough in Marin County, California suggest that immunity to pertussis wanes between immunizations, leaving children vulnerable to illness from about age 8 until their next scheduled booster at 11–12 years of age. As more people lose their immunity and become infected with whooping cough and other infectious diseases, everyone they contact is now vulnerable to infection.
Should parents be worried?
Measles is particularly concerning because it is highly contagious. In 1980, before vaccination was widespread, measles caused an estimated 2.6 million deaths annually, according to the World Health Organization (WHO). Fortunately, immunization has greatly reduced the number of measles deaths.
Pertussis or whooping cough is also highly contagious but typically results in far fewer deaths. (You can find more detailed information on whooping cough here.)
Infectious diseases are seldom cause for concern in otherwise healthy adults and children. On the other hand, the disease can be problematic in individuals with immature or impaired immune systems, such as babies and young children, resulting in serious illness and death.
Newborns are immune to many diseases because of the antibodies they received from their mothers, but young children do not have maternal immunity against some vaccine-preventable diseases, such as whooping cough, according to the CDC.
Ten California infants died of whooping cough in 2010. They were among the 9,143 cases of the disease reported in California that year—the highest prevalence in 63 years. Across the U.S., a total of 27,550 cases of the disease were reported. The CDC notes many more cases likely went undiagnosed or unreported.
A retrospective study of infants hospitalized for pertussis in Southern California from September 1, 2009–June 30, 2011 shows that white blood cell count (white blood cells fight disease and infection) can confirm whether children are suffering from pertussis and which children are at highest risk for serious complications, including death. The study showed infants with more severe cases of pertussis had higher white blood cell (WBC) counts (as well as faster heart rates and rapid respiratory rates) and were more likely to show at least a 50 percent increase in WBC within 48 hours of onset of symptoms. The study concludes WBC monitoring is a critical component in assessing not only the severity of the disease but also the need for intervention.
Similarly, in 2008, there were measles outbreaks reported in four states. Most of the cases occurred in unvaccinated individuals—13 of them were infants under 12 months of age (too young to be vaccinated routinely), and seven were toddlers ages 12–15 months (not yet vaccinated).
Fortunately, no one has died from measles in the U.S. since 2008. The CDC explains that 90 percent of the cases can be traced to other countries with lower immunization rates.
The prevalence of pertussis in the U.S. is increasing at an alarming rate. Because of this, the Centers for Disease Control and Prevention (CDC) in its 2013 immunization schedule recommends that all adolescents, as well as pregnant women, receive the Tdap (tetanus, diptheria, and pertussis) vaccine. The agency recommends that women receive a Tdap vaccine each time they are pregnant, ideally between 27 and 36 weeks of gestation. The American Academy of Pediatrics (AAP) concurs that pregnant women (as well as all other adults including those 65 and older) should receive the pertussis vaccine. However, the AAP has not confirmed that all pregnant women need a booster shot with every pregnancy. In its publication, the organization notes that it is “reviewing available information before publishing a policy statement concerning whether it is appropriate to provide additional Tdap doses for subsequent pregnancies.” Their findings will be published in a future AAP policy statement and in the 2014 immunization schedule.
The Tdap booster shot for pertussis enables older children and adults to maintain their immunity. Consider asking your health care provider if an additional pertussis booster would be beneficial when your child is between 8 and 12 years old. It’s essential that individuals who care for or live with children under the age of 1 year receive this vaccine. Pregnant women who have not been immunized are also at risk and should receive a single dose of whooping cough vaccine during their third trimester, late second trimester, or right after birth.
When family members and caregivers are immunized, children who are too young and individuals who are too sick to be vaccinated are protected as well.
Aside from getting fully vaccinated, the following steps will ensure that infants, older children, and adults are protected from these preventable diseases:
Last reviewed on January 29, 2013
Editor’s Note—June 7, 2013
New research adds support for Tdap during pregnancy, finding it to be more effective than postpartum Tdap and “cocooning” (vaccination of those in close contact with the infant) in reducing cases of whooping cough among infants, as well as subsequent hospitalizations and deaths. Study investigators estimate that vaccination during pregnancy would reduce incidence by 33 percent (compared with 20 percent for postpartum Tdap with cocooning), hospitalization by 38 percent (versus 19 percent) and deaths by 49 percent (versus 16 percent).
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