Harvard Health Letter

What you need to know about: vaccines

Now that flu season is here you may be scheduling your annual vaccination against influenza. But this can also be a good time see if all of your shots are up to date. It's important, since immunization to disease doesn't last a lifetime.

"Pretty much everything gets weaker as we age—our joints, heart, lungs, kidneys, brain. The same thing happens to our immune system," explains Dr. Paul Sax, clinical director of the division of infectious diseases at Brigham and Women's Hospital and a professor of medicine at Harvard Medical School.


The Centers for Disease Control and Prevention recommends an influenza vaccine annually for all adults. If you're concerned that flu shots don't work or make you sick, Dr. Sax suggests reconsidering. "Placebo studies show the vaccine doesn't really cause the flu. And while all vaccines may rarely cause side effects, the fact that essentially all infectious disease specialists get the vaccine shows that the benefits outweigh the risks," he says. Flu vaccine side effects include fever and aches as well as soreness, redness, or swelling where the shot was given.


If you wind up in the emergency room for a bad scrape, you'll likely be asked when you had your last tetanus shot. -Tetanus can cause your muscles to tighten (the most well known example is lock jaw). The -tetanus vaccine is usually given with the vaccine for diphtheria. You need a -tetanus booster every ten years. If you can't remember when you received your last -tetanus shot, it's still safe to get one even if it's been less than ten years. Common side effects include fever, redness and swelling at the injection site.


Vaccines for pneumococcal infection (which can lead to pneumonia) can protect against life-threatening pneumonia. All adults 65 or older should get this shot once (and a second time after age 65 if the first shot was when they were younger than 65). Adults who have conditions that weaken their immunity (such as HIV infection or chronic kidney disease) may need more than one shot. Common side effects include fever, muscle aches, and drowsiness.


Herpes zoster, also known as shingles, is a painful skin rash caused by the varicella zoster virus, which also causes chickenpox. The vaccine was recently approved by the Food and Drug Administration for people age 50 and older; however, the Advisory Committee on Immunization Practices continues to recommend that vaccination begin at age 60. Common side effects include soreness, redness, or swelling where the shot was given.