How Do Vaccines Work?

Vaccines have been around for a long time now, and thanks to them, many diseases that were once constant threats—diseases like polio, HIB, and measles—are all but extinct in many countries. After a few decades of regular use, vaccines may have left the spotlight for a bit—until COVID-19 arrived, that is. Now, with a pandemic raging around the world, vaccine development is at the forefront of everyone’s minds once again.

Immunizations can often be taken for granted, especially if you’ve gotten them your whole life and haven’t had to think much about the diseases they are preventing. When considering a new vaccine, people may have more questions about how vaccines work to keep illnesses from spreading. Here are some answers to questions about how vaccines fight diseases like COVID-19.

What Kinds of Vaccines Are Used?

All vaccines are not created equal. There are actually several different kinds of vaccines designed specifically for certain viruses. Some vaccines use an entire pathogen that has been killed (inactivated) or weakened. These include some well-known immunizations like hepatitis A, influenza, measles, mumps, and rubella.

Others, like the pertussis vaccine, use only certain parts of a pathogen. Today, some vaccines are even created using genetic material from the virus. This technique has been used in recent years as scientists worked to develop vaccines for Zika, avian influenza, H1N1 influenza, and others. All of these techniques have been explored in the development of a COVID-19 vaccine as well.

How Do Vaccines Fight Viruses?

Regardless of the method used for a particular vaccine, the goal is to help the body learn to fight off a pathogen on its own. When your immune system fights off an infection on its own, it can learn to recognize that pathogen. Vaccines cause an immune response and help the body to “remember” the disease. While you can develop immunity to a disease naturally if you become sick, that initial infection can result in serious symptoms, long-term side effects, and even death. A vaccine provides that immunity without suffering through the illness.

“Some people worry that getting a vaccine, such as a flu shot, could actually give them the virus,” says Cynthia Oliva, director of nursing at Cedar Crest Nursing and Rehabilitation Center. “While a person may experience minor side effects after an immunization, vaccines do not make people sick with the virus they are intended to fight.”

Why Do Some Vaccines Need Multiple Doses?

While some immunizations last a lifetime, not all do. Some vaccines—often inactivated vaccines—need more than one dose for full immunity. Other vaccines do not last forever and need boosters over time due to waning immunity, such as the pertussis vaccine.

The flu shot is a special case and needs to be taken annually. Children need more than one dose the first time, then a yearly vaccine because the immunity wanes over time. For children and adults, the flu vaccine is developed to fight the flu strains expected to circulate each year, and the vaccine can change from one year to the next.

Do Vaccines Affect Seniors Differently?

Vaccines can be less effective in elderly individuals because of a weakened immune response. Most of the research into vaccines and immunity for the elderly has involved the annual flu vaccine. Different forms of the flu vaccine have been developed to improve the effectiveness in seniors. Using a higher dose or a vaccine with an adjuvant that enhances the immune response has helped improve the protection for seniors against disease.

Vaccines can sound complicated, but the goal is simple: to protect you from disease. Getting immunized is the best way to help your immune system recognize and attack dangerous pathogens and keep you healthy.