How Vaccines Work

By: Alia Hoyt  | 

Adult Vaccinations

Adult (18-65): Adults should be revaccinated for any of the already-mentioned diseases if there's evidence of waning immunity. For example, when a woman becomes pregnant, her doctor usually runs tests to make sure that she's still immune to German measles. Also, not all adults have received every vaccine, either because they weren't available when they were children, or they were never immunized in the first place. Further, some vaccines have a limited life span. DTaP, TD (tetanus and diphtheria) and flu are common vaccinations or re-vaccinations for adults.

Elderly (over 65): Adults over age 65 are at an increased risk of complications from disease, simply because their immune systems aren't what they used to be. Pertussis, pneumococcus and the flu pose extra threats to this age group. The elderly should make sure that their vaccinations are up-to-date because some may have worn off over time. The following is also recommended:


  • Zoster (shingles) - Adults over age 60 should get the vaccine for herpes zoster (shingles). This painful disease causes a blistery rash.

High-risk groups: These are children and adults who don't have the best immune systems. These are usually people with compromised immune systems from diseases such as cancer. The schedule for these patients is largely controlled by their particular specialist and should be maintained because the disease can be harsher on them than others [source: CDC].

Vaccines aren't just for humans. Pets are lining up for shots to prevent illness and death as part of their annual check-ups. Experts agree that vaccines have protected millions of animals over the years. Pet owners should talk to a veterinarian about which vaccines are necessary (core) and which are optional (non-core), because there is some variation depending on where you live and whether or not your pet goes outdoors.

  • Canine core vaccines: distemper, parvovirus, hepatitis and rabies
  • Canine non-core: measles, canine adenovirus-2, parainfluenza, Bordetella, leptospirosis, coronavirus and Lyme
  • Feline core: distemper, feline viral rhinotracheitis, rabies feline and calicivirus
  • Feline non-core: feline leukemia, ringworm, feline infectious peritonitis, bordatella and chlamydia

Some debate is heating up between people who think that animals need yearly revaccinations and those that think it's unnecessary. Unfortunately, there's not enough evidence to prove beyond a reasonable doubt that immunity lasts more than a year.

Complete recommended vaccine schedules for dogs, cats and other animals are available here.

There can be confusion and misunderstanding about vaccines. On the next page we'll debunk some of the myths you might have heard.