by Karl O. A. Yu, M.D.
Many a parent has seen it. A baby is more cranky than usual. She might have a fever — or maybe not. Then, comes the ear-tugging. Invariably, this would lead to a trip to the pediatrician or an urgent care center. An ear infection is confirmed. Then, we take a trip to the pharmacy for a bottle of the pink stuff (the antibiotics) plus some kid’s ibuprofen to treat the pain.
Acute otitis media — a short-term infection of the space in the middle ear — is among the most common of infections seen in early childhood. Nine out of 10 kids will get an ear infection by age 2 — usually symptomatic, but sometimes not. Risk factors include contact with siblings or daycare, exposure to cigarette smoke, and a family history of recurrent ear infections. In the U.S., ear infections account for 12 million drug prescriptions a year, and healthcare and societal costs of more than $3 billion.
As a pediatrician, the story of how an ear infection occurs is one I’ve told over and over again. The Eustachian tube connects the throat to the chamber of the middle ear. We actually open this tube when we chew gum to help our ears “pop” when pressure builds up in an airplane. When a child has an upper respiratory infection — like a cold or the flu — bacteria that normally inhabit the back of the nose and throat can “march up” the Eustachian tube into the middle ear and set up shop. It doesn’t help that some viral infections — the flu virus, for instance — can weaken local immune cells that can otherwise fight germs effectively. Bacterial ear infections are treated with antibiotics, as untreated infections lead to more trouble. Repeated or chronic ear infections often lead to a visit to an ENT doctor and ear tubes.
The epidemiology of otitis media is quite fascinating. The older textbooks agree: the biggest player is a germ called Streptococcus pneumoniae. This germ comes in different serotypes — these are our way of identifying the carbohydrates that “coat” the bacteria — and immunity to one serotype does not protect against another. “Strep pneumo” is related to the germ that causes strep throat (this would be Streptococcus pyogenes, or group A strep). But, beyond ear infections, Strep pneumo is a major cause of life-threatening pneumonia, meningitis and sepsis in young children. It hits the elderly with pneumonia, as well.
Germ #2 is Hemophilus influenzae — though despite its name, this is not related to the flu virus. Like Strep pneumo, Hemophilus sometimes carries a capsule “coat” that helps it escape the immune system. Probably the most dangerous version of these bacteria is Hemophilus influenzae capsule type b, or “Hib.” While Hib can lead to ear infections, this is most importantly a cause of meningitis, sepsis, septic arthritis and epiglottitis. This last one — infection and swelling of the tissue by the opening of the windpipe — is the cause of many a horror story of a pediatric resident.
You see, I have never seen a case of Hib epiglottitis in my 9 years in pediatrics. Not one.
The reason? Better vaccines.
There have been vaccines using the capsule “coat” of Hib and Strep pneumo for decades, but they never worked well in babies. Infants’ immune systems are immature, and the capsule’s carbohydrates cannot elicit as good a response than the usual protein-type vaccines (like tetanus), as they cannot activate T cells. The 1990’s saw the development of conjugate vaccines against Hib and Strep pneumo. These are vaccines with the capsule carbohydrate stuck together with a “carrier” protein. As opposed to the older generation of vaccines, the conjugate vaccines work well in infants and young kids — the very group of patients at high risk of dying of Hib or Strep pneumo infections. And, as a point of local pride, researchers in Rochester helped develop the Hib vaccine.
These vaccines work! For U.S. children under age 5, life-threatening invasive infection due to Hib went down by 99%, and that of Strep pneumo by 76%. Interestingly, Hib and Strep pneumo infections in the elderly came down, as well — showing that if grandkids are healthier, their grandparents could be, too. And, while ear infections are rarely life-threatening, the medical and economic impact of having ear infections come down 20% is not to be sneezed at, either.
But, our tools remain limited. The Hib conjugate vaccine targets a single capsule — the b type. There are 6 other Hemophilus serotypes, and some bacteria have no capsule at all — the “nontypeable” Hemophilus. On the other hand, Strep pneumo has over 90 different serotypes. The current vaccine only covers the top 13.
Newly published research from 10-year-old Ear Immunity Study, conducted in Rochester General Hospital with community pediatricians and published this month in Pediatrics, have shown that while ear infections are coming down, the causes of infection are changing. Other “non-vaccine” serotypes of Strep pneumo, the nontypeable Hemophilus, and a third germ — Moraxella catarrhalis — are now the dominant causes of otitis media. Our use (and overuse) of antibiotics in the past century is catching up to us, as well. Half of Hemophilus strains are resistant to penicillin. All Moraxella are, as well.
This same research group has pioneered an old-turned-new way of managing ear infections, as well. A tympanocentesis, or “ear tap,” is when pus is drained from an infected middle ear. This is a skill pediatricians have lost — ear taps used to be done routinely by family physicians nearly a century ago before antibiotics were around. Testing ear tap fluid in the lab tells us what exact germ is causing a child’s infection and how to treat it more effectively. The Rochester experience shows that tapping infected ears lead to fewer kids with repeated ear infections or needing ear tubes.
The challenge remains. For the next version of Strep pneumo vaccines, which serotypes should we include? How do we design vaccines against the nontypeable Hemophilus and Moraxella? How else can we reduce ear infections? Would better vaccines against these germs also work against other kinds of infection, like pneumonia or sinusitis? Through the hard work of the nurses, doctors, and scientists in this research, and the efforts and bravery of the parent / child volunteers in the Ear Immunity Study, we look ahead with some hope. For information on the Ear Immunity Study, visit http://www.rcrclinical.com/ear-immunity/
Dr. Yu is a scientist, pediatrician and pediatric infectious disease specialist. He recently joined the Rochester General Hospital Research Institute as Assistant Director for the Center for Infectious Diseases and Immunology. His research focuses on the role of the immune system in childhood infections, while his clinical interests include primary immunodeficiencies and infections in immunocompromised children. He is a member of the Clinical Immunology Society and the Pediatric Infectious Diseases Society, and is a fellow of the American Academy of Pediatrics.