Why Do Some Vaccines Require Booster Shots? Here’s Why They Can Be Critical

It’s about reducing the risk of disease for everyone. 

Over the last few months, there’s been a lot of talk about COVID-19 booster shots. The U.S. Department of Health and Human Services (HHS) is now recommending that people get a COVID-19 booster shot eight months after they were first vaccinated — the rollout of those shots should begin in the fall. 

But let’s take a step back and talk about why vaccines can be important for your health, and why booster shots are sometimes necessary — whether that’s for your shingles vaccine, or the COVID-19 vaccine. 

What’s the history behind vaccines?

Vaccines have helped us get rid of some very scary diseases. In 1796, English doctor Edward Jenner first attempted control of an infectious disease by deliberate vaccination, for smallpox. Since then, vaccines have been developed by scientists from across the globe to fight polio, cholera, the plague, and more.

Doctors, scientists, and public health officials have worked together to understand when vaccines are most effective and who needs to receive them, creating the immunization schedule. Children, adults, and seniors are eligible for vaccines, which are an important part of preventive healthcare and staying healthy. While getting a vaccine is a personal decision, that choice affects other people in your community, by reducing the risk of disease for everyone. 

How do I know which vaccines I need? 

The vaccines you need often depend on your age, job, lifestyle, travel, or health conditions. While the Centers for Disease Control and Prevention (CDC) recommends that all eligible Americans get vaccinated, your doctor is the very best person to talk to about what’s right for you. You can fill out this questionnaire from the CDC and take it to your doctor to guide your conversation. 

Humana knows how important it is that older Americans stay on top of their vaccines and booster shots, especially since seniors have additional risks from infectious diseases. The CDC recommends specific vaccines for adults over 50, including vaccines to prevent shingles and pneumonia. 

Why do certain vaccines require a booster shot? 

A booster shot is an extra dose of a vaccine that helps your immune system create more antibodies to fight off disease and builds longer-term protection. Sometimes, protection from the original vaccine wears off over time, as with some childhood vaccines. In other cases, viruses change, or mutate, making the original vaccine less effective. 

The flu viruses are a good example: Our immune protections from a flu shot decline over time, and flu viruses are constantly changing. That’s why the CDC recommends yearly flu shots for most people 6 months and older, to build strong immunity and prevent illness. 

Even though vaccines have greatly reduced infectious diseases, the viruses and bacteria that caused these diseases are still out there — and they can still make you sick, especially if you aren’t vaccinated or need a booster shot. Read more about why vaccines are so important. 

What’s the latest on the COVID-19 booster shots? 

COVID-19 boosters will be an important part of our defense against the current pandemic. COVID vaccines reduce the likelihood of infection with the highly contagious Delta variant, and they’re very effective in preventing hospitalization and death from the variant. But new data shows the vaccines’ effectiveness wears off over time. That’s why HHS announced plans for COVID booster shots — to help vaccinated people maintain protection from severe COVID disease over the coming months.

Are vaccines safe?

There’s a lot of conflicting information available about the safety and effectiveness of vaccines, and you should know that some of it’s simply not true. If you take a good look at the evidence, it’s clear that vaccines and vaccine boosters are very safe. They’re tested and monitored through the Food and Drug Administration (FDA) and the CDC, which continually track the safety and effectiveness of licensed vaccines.

The FDA recently granted full approval for the Pfizer vaccine for people over 16 years old. The Moderna and Johnson & Johnson vaccines are authorized by the FDA for emergency use, and the Pfizer vaccine is approved for 12 to 15-year-olds — and as a third dose for some immunocompromised groups. 

Despite what you might’ve heard, vaccine side effects are usually mild (soreness, redness, swelling) and go away in a few days. Severe side effects are very rare, meaning that vaccines are one of the simplest ways to protect your health.

The cost of the jab

COVID-19 vaccines and boosters are free, regardless of health insurance or immigration status.

Other vaccines and boosters may be free via most health insurance plans, including Medicare, Medicare Advantage, and Medicaid. Check with your insurance company to see which vaccines are covered for you. And if your health plan doesn’t cover vaccines, Vaccinate Your Family can help you figure out how to pay for vaccination for you and your family members.

If you don’t have health insurance or a regular place to get care, a federally funded health center may be able to help you get vaccinated. Find a health center near you.

When and where do I get the vaccine?

Vaccines and boosters are generally available at your doctor’s office, pharmacies, community health clinics, health departments, and other locations, like schools and religious centers. 

COVID-19 boosters will be available first to those who are immunocompromised or were fully vaccinated earliest, like healthcare providers, nursing home residents, those with chronic conditions, and people over 65 years old. COVID-19 boosters will generally be available in the same places in your community as other vaccines. 

How much of a booster will you get? The Pfizer booster will be the same dose as the original shot, while Moderna has been testing full and half-dose shots. (Johnson & Johnson announced positive data on the effectiveness of the company’s booster shot just last week.) More details on the availability and timing of the boosters will soon be announced.

If you have questions about where to get a vaccine locally, contact your state health department.


This article is intended to provide general information about vaccines and booster shots. It is not meant to replace or be used in addition to the advice of health care professionals. If you have specific health care needs, or for complete information, please see a doctor or other health care provider.