QUESTION: You have mentioned the need for adults to be protected against various diseases. No one seems to have a general schedule for adult immunization. For example, what if one has not had tetanus protection since childhood? I don't even remember having it then. Am I a disaster waiting to happen? And what about adult polio protection? I'm confused. - S.Z.

ANSWER: Some potential illnesses demand lifelong immunization protection. Tetanus comes to mind immediately. You need to renew that protection every 10 years. It is usually incorporated into a shot for diphtheria, so you keep up with that at the same time.Some refer to the tetanus problem as lockjaw, a reference to the general muscle assault by the poison made by the infecting tetanus organism. We don't see very many cases of lockjaw today, and almost all occurrence is among older people who have permitted immunization to lapse. But believe me, each lockjaw case is a memorable experience.

Since the earliest tetanus shot is given at about five years, it is easy to remember a lifelong program based on 10-year age increments - 15-25-35-45... and so on. Researchers were shocked at the results of a survey of large numbers of older people regarding tetanus protection. The great majority were unprotected.

In addition to the tetanus/diphtheria matter, influenza protection is recommended for everyone 65 or older. But the 65 number has no magic about it. Anyone with chronic lung, heart or kidney illnesses should take pains to be protected, regardless of age. And the same applies to the pneumococcal pneumonia shot.

Polio is a special consideration. You ordinarily don't need this protection as an adult unless you have not had prior protection and are traveling to an area where polio is rampant. Some doctors advise parents to receive the dead polio vaccine routinely at the time their children are immunized with the live virus vaccine.

QUESTION: Please explain the difference, if any, between the exercise the heart gets through physical activity and the exercise it gets from beating fast from excitement, fear, etc. Some say that people under emotional stress might have as healthy hearts as those doing aerobic exercise. - Mrs. S.P.

ANSWER: The racing of the heart from fear or anxiety does not produce health benefits. The cause there is an outpouring of the adrenal gland hormone (adrenalin). This "fight or flight" situation can be harmful over time as the continued stimulation of adrenalin whips the heart into fruitless frenzy.

The elevated heartbeat from exercise arises from the extra blood demand being made by the exercising muscles. And that demand is strengthening the heart muscle itself without subjecting the body to the adrenalin surge. The fitness introduction material might explain the idea of aerobic benefits for you. Others may order it by writing: Dr. Donohue/No.12, Box 830, Gibbstown, NJ 08027-9909, enclosing a long, double-stamped, self-addressed envelope and $2.

QUESTION: I take the new pill, Cipro, for bladder infection. Why is it so expensive? Does it have other uses? - E.M.

ANSWER: Cipro (ciprofloxacin) is an antibiotic. It's a new drug and new drug costs reflect development costs. Yes, it's also used for a wide variety of non-urinary tract infections. If your bladder infection is "garden variety," there are other, cheaper antibiotics. Ask your doctor if one will do for you.

Dr. Donohue welcomes reader mail but regrets that, due to the tremendous volume received daily, he is unable to answer individual letters. Readers' questions are incorporated in his column whenever possible.