A rise in reported whooping cough, or pertussis, cases this year has the Centers for Disease Control and Prevention (CDC) predicting that 2012 will have the highest number of cases since 1959. Several factors have contributed to this rise in whooping cough, and researchers and officials are working to educate the public on prevention, as well as find new ways to enhance the effectiveness of the vaccine.
What is whooping cough?
Whooping cough is a highly contagious bacterial infection, Bordetella pertussis, that is spread by airborne droplets of fluid after coughing or sneezing. The bacteria affects the lining of the trachea and bronchi - the windpipe and two airways that branch out to the lungs. Early symptoms of pertussis are similar to a cold, with runny or congested nose, a feeling of malaise, a slight fever, sore throat, sneezing, watery eyes and a dry cough.
These signs typically last for a couple of weeks before symptoms worsen. In later stages, whooping cough causes severe episodes of coughing with phlegm and a “whoop” sound as the person gasps for air. Coughing episodes can last for two minutes, with several episodes occurring one after the other. These symptoms can last over two weeks, even after treatment.
Babies and young children may not make a whooping sound after the cough, and may instead gasp, gag or even stop breathing. This can become so severe that the child dies. So far this year nine children have died from whooping cough, according to NBC news.
Severe symptoms are less common in older children, adults and people who have been vaccinated.
Who is at risk?
Babies and young children are most at risk for whooping cough, particularly babies and children who have not been vaccinated, says Kathryn Edwards, M.D., professor of pediatrics at Vanderbilt University, and secretary of the Infectious Disease Society of America.
Dr. Edwards, an infectious disease specialist in pediatrics, has been working on the whooping cough vaccine for many years. “One vulnerability is that we are not able to vaccinate before six weeks of age,” she says.
Why is whooping cough in the news?
According to the CDC, 18,000 cases of whooping cough have been reported already this year, which is over double the total recorded for 2011 and is now considered an epidemic. In addition, some states have experienced a sharp rise in cases. Washington State has seen a 1,300 percent increase in cases during the first six months of 2011, and it declared a state of emergency in April. Several other states have also seen an uptick in cases, including Wisconsin, New York, Kansas, Arizona, Minnesota and Colorado.
Why is the rate so high?
There are a number of factors contributing to the high rates of whooping cough, says Dr. Edwards. “We now have a greater appreciation that the youngest children are always at the greatest risk for whooping cough, particularly the ones so young that they haven’t been vaccinated.”
Since children cannot be vaccinated earlier than 6 weeks of age, Dr. Edwards says adults have a major role in spreading whooping cough to children. “Studies show that a half to three-fourths of cases of whooping cough acquired by babies come from their families.”
Even adults who have been vaccinated have waning immunity, and most adults have not been vaccinated since they were 4 to 6 years of age, she says.
Another issue is there are pockets of the country where children aren’t being vaccinated, which is why Washington State has seen so many new cases of pertussis. “Because there are large rates of no vaccination, even vaccinated kids are at higher risk because of circulation of the disease,” says Dr. Edwards.
Another contributing factor is that antibodies provided to the baby at birth are very low, says Dr. Edwards, “There is not much protection from mother to baby at birth.”
Furthermore, about 20 years ago there was a great deal of concern about the whooping cough vaccine. At the time, a whole pertussis germ was activated and used in the vaccine. “Although it was very effective, it was associated with a fair number of local symptoms and fever and a lot of parents were worried about the vaccine,” says Dr. Edwards.
Because of this concern, researchers at the NIH, pharmaceutical companies and Dr. Edwards herself became very involved in testing the vaccine. They began using an acellular vaccine, which is a more highly purified version of the whole cell that was used before. Essentially, it uses activated proteins from whooping cough rather than the whole cell, says Dr. Edwards.
The new vaccine hit the market in 1997, and though it is effective, the duration of protection appears to be shorter than the earlier vaccine.
“Those of us who spent our life in the trenches trying to make safer, less reactive vaccines, I think this comes as a bit of a disappointment, that duration of protection is not as long, “ says Dr. Edwards.
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What can we do to prevent it?
There are several options on the horizon that will give us better control of whooping cough, says Dr. Edwards. First, is increasing the rate of vaccination in adults. “There are billboards and pharmacies advertising for TDAP [whooping cough vaccine],” says Dr. Edwards. “We hope that we can decrease the burden of contagion for pertussis and make children less susceptible.”
In addition, pregnant women should be getting vaccinated in the second or third trimester to give antibodies to their baby until they are old enough to get vaccinated. Unfortunately, pregnant women are not eager to get vaccinations, which can be “a bit of a challenge,” says Dr. Edwards. “Mothers who are not vaccinated during pregnancy should be vaccinated post-partem to protect themselves, and thus, their babies.”
Another way to prevent pertussis is to give earlier doses of the booster vaccine. Currently, children get a booster at 12-13 years of age, with five shots total, but that may need to be bumped up to 10 years of age, says Dr. Edwards.
Targeting pediatric and obstetrics healthcare workers for the vaccine and figuring out how often they need boosters is also important. They could be giving whooping cough to the people they treat or the babies they deliver, says Dr. Edwards.
Current and future research could also hold the key to enhancing the effectiveness of the vaccine. A new vaccine in France uses a live weakened pertussis strain that is given through the nose. There are also antigen enhancers that can create higher antibodies, or possibly a whole cell vaccine that is less reactive, but gets more duration.
Another piece of the puzzle is to work with the health department and media to spread the word about the importance of the vaccine, says Dr. Edwards. “People need to understand what is at stake.”
Christian Nordqvist. (2012, July 22). "Whooping Cough Worst Year Since 1959, Says CDC, USA." Medical News Today. Retrieved from http://www.medicalnewstoday.com/articles/248135.php.
Maggie Fox. (2012, July 22). “CDC: Whooping cough epidemic worst in 50 years.” NBC News. Retrieved from http://vitals.nbcnews.com/_news/2012/07/19/12835335-cdc-whooping-cough-epidemic-worst-in-50-years?lite
Published On: July 31, 2012