A close up on a syringe drawing vaccine from a vial.

A s we age, the immune system slows down, chronic conditions become more common, and the body may be less able to fight off infection and more vulnerable to its complications.

That’s where vaccines come in. These immunity boosters help prevent serious diseases at any age.

“Vaccines are not only for kids or teens,” says David Kim, M.D., director of the National Vaccine Program of the U.S. Department of Health and Human Services. “If you’re older, you’re at a higher risk for certain vaccine-preventable diseases.”

Here are the shots you may need, when to get them, and why they’re critical for keeping you and your loved ones healthy.

Flu Shot

Who needs it, and when: All adults need a flu shot every year, ideally sometime in October, before flu season. But if you don't get it then, just do it as soon as you can. The protection offered by the shot takes two weeks to fully kick in.

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Why: Most people recover from the flu. But older adults are at the greatest risk for severe complications, such as pneumonia. The flu shot isn’t perfect—last season’s vaccine was just 29 percent effective overall, and only 12 percent effective for people 65 and older—but research shows that if you do get the flu, being vaccinated reduces your risk of serious illness.

Remember: Two versions of the vaccine are available specifically to people 65 and older: Fluzone High-Dose and Fluad. They're designed to produce a more robust immune response in older adults. Still, the Centers for Disease Control and Preven­tion says the most important thing for older adults is that they get the flu shot by the end of October, before flu season begins. So don't delay getting vaccinated with the shot that is available if Fluzone High-Dose or Fluad isn't in stock at your pharmacy.

Pneumonia Vaccine

Who needs it, and when: All adults should get the vaccine known as PPSV23 (Pneumovax 23) once they turn 65. Talk to your doctor about whether you should also get PVC13 (Prevnar 13) for added protection (more on this below).

Why: These vaccines protect against pneumococcal bacteria, which can cause pneumonia and other illnesses, such as meningitis. In older adults, these illnesses can lead to serious disease and even death. (Pneumonia, for example, kills 1 in 20 older adults who get it.) Pneumovax 23 is 50 to 85 percent effective at preventing serious disease from these bacteria, according to the CDC.

Remember: Prevnar 13, one of the pneumococcal vaccines, used to be recommended for all older adults in addition to Pneumovax 23. But recently, the CDC’s expert vaccine panel voted to take it off the list of shots that all older adults should routinely get. Data shows that routinely giving children Prevnar 13 indirectly protects seniors too, so vaccinating older adults isn't always necessary. Talk to your doctor to see whether you might benefit from Prevnar 13.

Shingles Vaccine

Who needs it, and when: Everyone 50 and older should get the shingles vaccine Shingrix, which is given in two doses separated by two to six months. (If you’ve had Zostavax, the older shingles vaccine, you should still get Shingrix.)

Why: Shingrix is 97 percent effective at preventing shingles in people ages 50 to 69 and 91 percent effective in people 70 and older. It’s also highly effective at preventing postherpetic neuralgia (PHN), a complication of shingles that can cause excruciating pain that can last for months or years.

Remember: The U.S. continues to experience a shortage of Shingrix because demand for the shot is so high. You may need to hunt around to find a dose. Try the CDC’s vaccine finder tool. And be sure to call the doctor or pharmacist before you visit to make sure the shot is really in stock. If it isn't, check to see whether you can be put on a wait list for when more doses are available. (In the interim, it’s an option to receive Zostavax—although it may also be unavailable, and Shingrix is preferred.)

Tdap Vaccine

Who needs it, and when: Older adults need a single dose of Tdap for protection against pertussis (whooping cough) if they've never had one before. A dose of Tdap has been recommended for all adults since 2005, but only about 20 percent of older adults have ever received it, according to the CDC. So check with your doctor to make sure you get this booster.

Why: Children receive vaccinations against whooping cough. But research has shown that immunity to pertussis, which can cause fits of violent coughing, wanes as you age. A dose of Tdap can increase your immunity. It’s about 70 percent effective against pertussis for the first year, then about 30 to 40 percent effective after four years.

Remember: Although pertussis can cause serious illness in adults, the infection is most worrisome for babies. That means it's important to get your dose of Tdap at least two weeks before coming into any contact with newborn babies. Getting yourself vaccinated can help keep you from spreading pertussis to an infant.

Measles Booster

Who needs it, and when: Anyone born in or after 1957 who doesn't have documented evidence of immunity to measles should get a dose of MMR, the vaccine that protects against measles, mumps, and rubella. Evidence of immunity can take the form of vaccination records or the results of blood tests for measles immunity.

Why: The CDC considers anyone born before 1957 to be immune to measles. Most adults who aren't immune need only one dose of MMR to be protected—but certain groups at high risk for the disease are the exception. If you're a healthcare worker or are planning any international travel, talk with your doctor about whether you might benefit from an extra dose of MMR.

Remember: A small number of people who were vaccinated for measles between 1963 and 1967 received a type of vaccine that is no longer used. Anyone vaccinated in those years should get revaccinated with today’s shot. If you don't have a vaccination record and aren't sure when you had your shots, it's usually easier to get an extra dose.

Editor’s Note: This article also appeared in the November 2019 issue of Consumer Reports On Health