Q. With all this talk about possible vaccine hazards, I just read that tetanus shots given to prevent a dangerous disease called lockjaw may also reduce the chance of getting multiple sclerosis. Is this true? My uncle has MS, and it's nasty — clumsiness, trouble urinating, poor vision and muscle weakness. And it's incurable.

A. Yes, MS is bad news, and often hits folks in their 20s or 30s. Its cause is unknown.

The tetanus story began years ago from allegations (never substantiated) that hepatitis B shots caused MS. More studies on hepatitis B were done, and one showed something intriguing — tetanus shots seemed to reduce MS risk. In 2005, Dr. Thomas Verstraeten and others from the Centers for Disease Control and Prevention found other studies showing the same result. Furthermore, they found that those with MS had reduced immunity to the tetanus toxoid found in tetanus shots, implying that immunity to tetanus protected folks against MS.

How so? Turns out that on the molecular level, tetanus toxoid looks like a special lymphocyte called the T-helper cell, important in auto-immune diseases like MS, and by getting tetanus shots, specific antibodies are created that could perhaps nudge the immune system balance from a pro-inflammatory to a more favorable anti-inflammatory state and thereby prevent MS from developing.

Just last month, Dr. Miguel Hernan and others did a systematic review in the journal Neurology and found nine studies that, taken together, showed tetanus shots may reduce the chance of getting MS by one-third. Another source, the Vaccine Safety Datalink project, found that while one tetanus shot reduced MS risk by 37 percent, two shots reduced it by 58 percent, and three or more by 77 percent.

By age 6, kids should have gotten five tetanus shots (combined with diphtheria and pertussis as the DPT vaccine). In adults with MS, a study by Dr. Christian Confavreux and associates found that those who got tetanus in combination with diphtheria or polio immunizations may relapse less often.

So get your Td (tetanus and diphtheria) shot every 10 years. Diphtheria can cause breathing problems and damage the heart and brain. If you're younger than 65, see if your doctor can substitute a new vaccine, Tdap (ap stands for acellular pertussis), especially if you're a healthcare worker or expect to have close contact with an infant younger than 12 months (like new parents) so that neither you nor they get pertussis or whooping cough, a violent, sometimes fatal cough that lasts for months. In 2004, there were more than 25,000 cases of pertussis in the U.S.

Dr. Landis Lum is a family practice physician for Kaiser Permanente and an associate clinical professor at the University of Hawai'i John A. Burns School of Medicine. Send your questions to Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; fax 535-8170; or write islandlife@honoluluadvertiser.com. This column is not intended to provide medical advice.