What's a vaccine?

The topic of vaccines always seems to be relevant — and may sometimes be a subject of misinformation. Before vaccines, infectious diseases like smallpox, polio and measles ran rampant.1 But thanks to medical advances, there are available vaccines to help protect us. A vaccine is a small dose of germs that’s meant to mimic a certain illness. This helps your body remember and recognize that infection and helps create antibodies to fight it off — keeping you healthy.2

A vaccine works kind of like it's “practice” for your immune system. Each time you get a vaccine, your body may get better and better at fighting off that particular strain of illness. Until one day, your immune system spots that illness and the antibodies go into action. Depending on the illness, you may need a different number of vaccines and timing to prevent illness.

What’s the difference between vaccine and immunization?

There’s a lot of medical terminology out there. And many terms may mean the same thing, which is the case here. A vaccine is something that may fire up your immune system so it can produce immunity to a specific illness. It’s usually given through an injection (like your annual flu shot). A vaccination or immunization (often used interchangeably) is simply the act of giving a vaccine. And once you have immunity to a specific illness, you may be protected from getting it even if exposed.2

How does herd immunity work?

Herd immunity is used by the Centers for Disease Control and Prevention (CDC) to describe when enough people within a single community become immune to an infectious disease through vaccination or from previous illness. This may slow the spread of disease and even might make it unlikely to spread at all.3 The percentage of people who may need to have protection in order to achieve herd immunity may vary by disease.

Common vaccines and when to get them

There are a several vaccines for infectious diseases or illnesses you may be familiar with. It’s recommended by the CDC that certain vaccines are given at certain ages, or for unique circumstances (like traveling abroad). Here’s a list of common vaccines:4

  • Chickenpox

  • Hepatitis A and B

  • Human Papillomavirus

  • Flu

  • Measles

  • Mumps

  • Polio

  • Shingles

  • Smallpox

  • Tetanus

  • Whooping Cough

You likely already got the majority of common vaccines when you were younger (like chickenpox, measles and mumps). As you get older, your doctor may let you know when it’s time for your next one. And before you take a trip out of the country, ask your doctor if there are recommended vaccines based on your travel destinations. You may want to keep track of what vaccines you have received and when you need your next dose to complete a series.

Child vaccines

Did you know child vaccines help protect against 16 diseases?5 It’s important to stay on top of your little one’s vaccines, ask any questions you may have and know where to go for more information. Be sure to schedule regular child well visits starting at birth to keep your child up-to-date on immunizations.

Learn what you need to know about child immunizations

Flu shots

It's recommended to get a flu shot every year to protect you and your family.6 If you have a UnitedHealthcare health plan, you can get a flu shot at more than 50,000 locations.

Learn more about flu shots and find a location

Pneumonia vaccines

It’s recommended that kids younger than 2, adults older than 65 and some individuals with certain underlying health conditions get the pneumonia vaccine. Learn more about the pneumonia vaccine and find out how to get it if you or a loved one may need it.

Find out more about pneumonia vaccines

COVID-19 vaccines

COVID-19 vaccines are an important step in slowing the spread of the disease. Review the current information to help you stay informed on COVID-19 vaccines and discuss any questions you may have with your health care provider.

What to know about COVID-19 vaccines

What kind of doctor should I see for my vaccines?

Vaccines can be administered by doctors, nurses and pharmacists. Typically, when you visit your primary care provider for your yearly exam, your doctor will check your chart to make sure you’re up-to-date on any regularly scheduled vaccines. You may also need to catch up on any doses you may have missed between now and your last visit. Making a special trip for flu season? Many walk-in clinics, pharmacies, or even schools will likely offer flu vaccines.7 If you’ve got that next international trip planned, be sure to talk with your doctor about where you’re headed in case you may need a few more vaccines before you travel.

Find a doctor

Review our adult vaccines checklist

You can use this adult vaccines checklist to help prepare for your next doctor visit. Ask your provider which vaccines may be right for you. 

  • Influenza vaccine. Annual immunizations are the best way to prevent the flu.
  • Tdap or Td vaccine. Tdap protects against tetanus (lockjaw), diphtheria and pertussis (whooping cough). Td protects against tetanus and diphtheria.
  • MMR vaccine. Protects against measles, mumps and rubella (German measles).
  • Pneumococcal vaccines. Protect against illnesses such as pneumonia.
  • Hepatitis A and B vaccines. Protect against serious liver diseases.
  • Hib vaccine. Protects against a dangerous bacterial disease called Haemophilus influenzae type b (Hib).
  • HPV vaccines. Protect against human papillomavirus. Certain types of this virus cause cervical and other cancers. The vaccines are recommended for preteens. But young adults may still need them if they didn’t get vaccinated as kids.
  • Meningococcal vaccine. Protects against meningitis and blood infections. It’s particularly important for college students who will be living in residence halls and people with certain health conditions.
  • Varicella vaccine. Protects against chickenpox. You may need it if you haven’t had chickenpox before or weren’t vaccinated as a child.
  • Shingles (zoster) vaccine. Protects against a painful skin rash. It’s generally recommended for adults 60 and older. (Note: Most plans don’t cover it before age 60, but there are some exceptions.)