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DEAR DR. ROACH: I am a 77-year-old female in good health. I am up to date on all vaccines, but I would like to know why after each COVID shot (about every six months), I have a debilitating reaction with flu-like symptoms. I ache all over, including my joints. This lasts for one to two days after the shot, and it's the only vaccine I react to. (Most of them have been Moderna.)

Why can't my immune system kick in by now and prevent these reactions? Also, my pharmacist's advice has been mixed as to whether it is okay to take 500 mg of Tylenol to reduce symptoms. -- K.W.

ANSWER: The problem isn't that your immune system isn't working; it's working a little too well for your comfort but very well for your safety. The common side effect of muscle and joint aches with other flu-like symptoms (sometimes including a low-grade fever) is, in fact, caused by your immune and inflammatory systems responding to the vaccine.

The vaccine causes your body to make a small amount of COVID protein, which your body recognizes as foreign and destroys. Before it destroys it, however, it "learns" to recognize the protein as an invader and gets better at responding to it.

This way, if your body sees COVID again (or even a closely related variant), it can respond to it and hopefully keep you from getting sick -- or at least keeping you from getting sick enough to need the hospital. The COVID vaccine has been proven to be effective at reducing severe illness, even if it isn't 100% effective at preventing illness completely.

Acetaminophen (Tylenol) has a theoretical risk of impairing the body's response to the vaccine when taken beforehand, although two well-done studies found that Tylenol did not reduce the body's antibody response to the vaccine. Some authorities still recommend taking Tylenol to prevent a reaction, but there is no reason at all not to take Tylenol to reduce the symptoms of a vaccine reaction.

Many of my patients are asking me whether they need to take a booster this spring, and I am recommending a spring vaccination in my most at-risk patients, such as those who are over 75 or who have any kind of chronic heart, lung or immune system disease.

DEAR DR. ROACH: I read your recent column on measles and polio, but my question is about mumps. I was born in1950. I had measles and chickenpox and was vaccinated against polio somwehere between 1955-1957. I caught rubella in 1968, but I never had mumps. So, do I need to get the MMR vaccine? Like other boomers, I don't want to suffer from any childhood diseases in my old age. -- A.Z.

ANSWER: Nearly everyone born before 1957 had measles and mumps (but not rubella, also called German measles) and should have lifetime immunity. (Estimates range from 95% to 99.5%.) Many people had the disease at a very young age where it might not have been recognized. Even if the blood levels of immunity (antibody titers) are low, most people who had the disease are still protected as they have memory cells that are capable of beginning the immune response.

For this reason, I don't recommend an MMR vaccine in your case. (Plus there are vaccine shortages in some areas as I write this.) People who are likely to be exposed in an ongoing outbreak, such as health care workers, should have their titers checked and get revaccinated if the test comes out negative, just to be safe.

Mumps is a relatively benign disease, but it does have a dangerous complication for men called orchitis, which is extremely painful.

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.

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