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Conversations with the Director: Thomas Clark, MD, MPH

July 11, 2013

Photo: Dr. Tom Frieden with Dr. Thomas Clark

Epidemiology Is Much More Fun Than When I Learned About It In Medical School: A Conversation with Thomas Clark, MD, MPH, Meningitis and Vaccine Preventable Diseases Branch, Division of Bacterial Diseases, NCIRD

When Clark, began his preventive medicine residency at Oregon Health Sciences University, he had a startling realization—that epidemiology was fun—much more fun than when he learned about it in medical school. CDC Director Tom Frieden, MD, MPH, is an ardent lover of the science of epidemiology, so hearing about this medical school experience during a recent Conversation with the Director discussion was a blow to his heart. “Well, you obviously didn’t have a good teacher,” Frieden said with a smile, trying to bring some sense to the notion that epidemiology could ever be anything but exciting.

Clark’s positive experience in Portland drew him to CDC where he spent his next two years as an Epidemic Intelligence Service officer in the then Mycotic Diseases Branch within the Division of Bacterial and Mycotic Diseases. Today, Clark is the epidemiology team leader for the Meningitis and Vaccine Preventable Diseases Branch within the Division of Bacterial Disease in NCIRD, helping protect people at home and abroad from bacterial meningitis, diphtheria, tetanus, and pertussis. “I tell people that 100 percent of our work is domestic and the other 100 percent is global,” Clark joked with Frieden when asked about the branch’s initiatives.

Recent Resurgence of Pertussis

In the past few years, there has been a resurgence of pertussis, or whooping cough, and Clark and his team are trying to better understand why and how CDC can help regain control over this public health threat. In China, pertussis is known as the “100 day cough.” It is a highly contagious bacterial disease that can present itself as a “nasty cold” and can take those infected “weeks to get back to 100 percent,” Clark discussed with Frieden. For infants who are too young to be vaccinated against it, pertussis can lead to hospitalization and even death—a major reason why effectively diagnosing and, more importantly, preventing the disease are CDC initiatives in the US and oversees.

The challenge with pertussis, Clark explained to Frieden, is that the tools used to detect it and the vaccines used to prevent it are less than perfect. Culture and PCR are good ways to test for the disease early in its course; however, it is often first misidentified as a bad cold in people who have been vaccinated. Serology can be used to detect pertussis later in its course, but the many tests commercially available have unknown clinical accuracy. Frieden asked, “Are we at CDC doing anything to improve vaccination?”

“We’re trying to better understand the effectiveness of the current acellular vaccines [DTaP and Tdap], which seem to not protect as well or for as long as the older whole-cell vaccines,” responded Clark. While the current adolescent and adult vaccines are only 70 percent effective, he explained, they are still our best bet in protecting those most vulnerable—infants and pregnant women. Unfortunately, fewer than five percent of pregnant women get the needed booster vaccine (Tdap), which is now recommended during the third trimester of pregnancy. “We’re working with the obstetrics community to get them to view themselves as vaccinators,” said Clark. “Yes, vaccination benefits moms, but, more importantly, it benefits babies in their critical first two months before they start their own vaccinations.”

Toward the end of their conversation, Clark opened up to Frieden about what keeps him coming to work at CDC. “There’s immediate impact in the work that we do around vaccine-preventable diseases,” he said, offering the recent pertussis epidemic in Washington state as an example. Clark and his team quickly recognized an increase in disease cases among Washington’s adolescents despite high rates of vaccination—suggesting early warning of immunity from the acellular vaccines and offering a possible explanation for increased population-level susceptibility to pertussis. With this knowledge in hand, Clark and colleagues worked with Washington’s health department to bolster vaccination efforts and saw a 140 percent increase in Tdap receipt among adults. (Read the MMWR article here). “It’s rewarding to get data in real time and inform public health decisions in real time,” said Clark. And both Frieden and Clark agreed that that is great fun.

This Snapshot article by Jessica Podlaski.