Dec. 23, 1998 By Melanie Fridl Ross
GAINESVILLE, Fla.---Two out of three senior citizens may lack adequate immunity to tetanus, a life-threatening central nervous system ailment contracted when bacteria invade an open wound, usually a deep puncture or cut made by a nail or a knife, University of Florida researchers report in the journal Clinical and Diagnostic Laboratory Immunology.
The findings suggest older Americans are failing to comply with immunization guidelines recommending tetanus boosters at 10-year intervals throughout adult life, said Dr. Desmond Schatz, an associate professor of pediatric endocrinology at UF's College of Medicine and the first author of a paper that describes a five-year study of the issue.
"The bottom line is that tetanus vaccinations are protective against the development of the disease and what is needed is a follow-up vaccination every 10 years to protect against it," Schatz said. "What we are finding is there are certain people-- particularly older people -- who haven't had the vaccinations every 10 years. That puts them at risk for getting the disease and suffering its devastating consequences."
Tetanus, also known as lockjaw, causes painful muscle spasms and is associated with a high death rate. Symptoms include a stiff jaw and neck, difficulty swallowing, muscle rigidity, fever, sweating and rapid heart rate.
Young children receive the DTP vaccine to protect against tetanus and two other diseases, diphtheria and whooping cough. But whether adults should receive routine booster shots to protect against tetanus has been the subject of much debate, with some experts arguing that the disease's increasing rarity and the medical costs associated with vaccination programs do not merit the practice.
Only 40 to 60 cases of tetanus are reported annually, according to the Centers for Disease Control. Most occur in individuals older than 50 who are unvaccinated or whose history of vaccination is unknown.
"The classic situation is you're out in the garden, you drive a nail through your finger or somebody hits you with a golf club and you need stitches," said Mark Atkinson, the study's senior investigator and an associate professor of pathology and medicine and director of UF's Center for Immunology and Transplantation. "Some say we're spending an awful lot of money as a society to protect against the relatively rare event. But if you get a tetanus infection, it's a real painful, very tragic end."
UF researchers studied blood samples taken from 461 randomly selected individuals ages 2 to 73 who were evaluated at UF outpatient clinics and UF's Clinical Research Center from 1992 to 1997. Eighty-two percent of children 2 years and older had cell-mediated immunity to the tetanus toxoid but immunity declined dramatically starting around the age of 41. Less than 30 percent of study participants older than 60 were immune to tetanus. Study participants' immunization histories were not available.
Researchers evaluated participants' so-called "immunological memory," the ability of their white blood cells to recognize rapidly the tetanus toxoid as a foreign invader and direct the immune system's cellular defenses to launch a swift attack.
"It's white blood cells that actually have to get the whole immune process rolling," Schatz said. "They're the ones that have the memory. If you immunize an individual with a vaccine for measles, it's the white blood cells that have the memory that they were once immunized against measles. So we analyzed the level of white blood cell reactivity against tetanus as a function of age."
The UF team's recommendation? Boosters for elderly individuals who already completed a primary immunization regimen, and a primary series of tetanus shots for those who are unvaccinated. Prevention is always better than cure, Schatz said.
"I think we need to put on our hats and be complete doctors," he said. "That includes the prevention of -not just the cure of -- disease."
The study helps focus attention on the need to step up the nation's immunization efforts in adults, said Dr. Douglas Barrett, a UF pediatrician and infectious disease expert.
"It's very clear that vaccination programs are one of the most dramatic and cost-effective advances that have been made in medical research in the last 50 years," said Barrett, who holds the Nemours chair in pediatrics at UF's College of Medicine. "Think about having eradicated smallpox from the face of the earth. Polio also has been abolished in certain countries. We have seen a 90 percent decrease in certain forms of childhood meningitis in the United States. All of those advances are a direct result of effective immunization programs. These are medical miracles. "
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