Lyme Disease: Where's the Vaccine?
July 8, 2011
With summer upon us, ticks are out again, and that's a problem for anyone who enjoys the great outdoors.
Scientists are pushing for the development of a new vaccine for Lyme disease.
A first-generation vaccine worked pretty well but was pulled from the market in 2002.
The number of Lyme disease cases has been increasing every year.
It's tick season again, which means it's also Lyme disease season, and that puts outdoorsy people on edge.
The tick-borne illness, after all, brings fevers, aches and other nasty symptoms that, for about 10 percent of victims, last for months or more.
Doctors know a lot about Lyme and the bacteria that transmit it. Yet, there is no human vaccine for the disease -- at least not anymore. While there is a highly effective vaccine available for dogs, a series of unfortunate events doomed a first-generation human vaccine, which was pulled from the market in 2002.
As numbers of Lyme cases continue to rise each year, some scientists are pushing to bring back a Lyme vaccine, either in its old form or in a new one. Failing to offer a vaccine, they say, is failing the many millions of people who live in the vicinity of deer ticks.
"In my opinion, this is a public health fiasco," said Stanley A. Plotkin, a pediatrician and infectious disease specialist at the University of Pennsylvania, Philadelphia. "There are well over 20,000 annual cases of Lyme disease and probably more than that. When else do you have a disease with that incidence where you know you can prevent it with a vaccine, but you don't make it?"
Cases of diagnosed Lyme Disease have steadily risen in the United States, according to data collected by the Centers for Disease Control and Prevention, from just over 10,000 confirmed illnesses in 1995 to at least 30,000 in 2009. Better surveillance explains some of that trend, said Paul Mead, a medical epidemiologist at the CDC in Ft. Collins, Colo. But numbers are certainly not going down.
In 2009, 95 percent of Lyme's cases occurred in just 12 states, mostly in the Northeast and Upper Midwest. Even so, Lyme was the sixth most common infectious disease in the country that year, below chlamydia and gonorrhea, but comparable in number to AIDS, and above hepatitis and tuberculosis.
Despite recommendations to use repellents and to do daily tick checks with a partner, however, case reports continue to climb.
"The prevention of Lyme disease is a very frustrating undertaking in the world of communicable diseases," Mead said. "I think we're open to anything that would be helpful in terms of trying to control the disease."
There used to be more options. In 1998, the pharmaceutical company SmithKline Beecham (now GlaxoSmithKline) released a Lyme vaccine that showed promise.
The vaccine was made from a single protein found on the surface of Borrelia burgdorferi, the bacterium that causes Lyme. When given to people, the vaccine prompted the production of antibodies that then entered ticks as they sucked vaccinated blood.
Instead of killing pathogenic bacteria in the human body, like other vaccines do, these Lyme antibodies actually immunized the insects by killing bacteria in their bodies. The vaccine was shown to prevent Lyme in about 80 percent of exposed adults.
Trials were underway to determine how often people would need to get booster shots. Scientists were also monitoring vaccinated children, who are more prone to tick bites and, along with older people, are most susceptible to Lyme. And results were encouraging, Plotkin said. Then, things started to go downhill for the vaccine.
First, some research started to raise questions about the bacterial protein that formed the basis of the vaccine, suggesting that sensitivity to the protein might explain arthritis and other symptoms that show up in cases of chronic Lyme disease.
Subsequent trials disproved the link. But that didn't matter to patient groups, who became convinced that the vaccine was responsible for causing the disease and chronic symptoms. Class-action lawsuits followed along with plenty of bad publicity.
When the vaccine was available, public health organizations like the CDC recommended it, added Gary Wormser, chief of infectious diseases at New York Medical College in Valhalla. But they didn't aggressively endorse it, which also contributed to low public demand. In 2002, GlaxoSmithKline decided to stop making the vaccine.
"A number of us wrote a letter to several pharmaceutical companies saying this is needed," said Wormser, who also edited a supplement in February's issue of the journal Clinical Infectious Diseases, which highlighted the need for a new Lyme vaccine.
Another pharmaceutical company, Baxter, has told him they are still working on developing a new Lyme vaccine, Wormser said. In other avenues of ongoing research, he added, some scientists are looking for ways to orally immunize mice, reducing their contribution to the spread of the disease. Other scientists are investigating vaccines that would make human blood taste bad to ticks.
"It's not like we don't have the science available to us and the technology to develop a second-generation vaccine that should work," Wormser said. "I don't think that's the problem. It's just a question of investing in it and finding a company wanting to do that."