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Understanding How Vaccines Work | RMHP Blog

Understanding How Vaccines Work | RMHP Blog



How Do Vaccines Prevent Illness?

The scientific and medical communities are working tirelessly to develop a vaccine for the novel coronavirus (SARS-CoV-2) that causes COVID-19. But how exactly do vaccines work?

Below we discuss why vaccines work, how they're made, and other key details.

How our bodies fight infection

To understand vaccines, you need to know how the body fights infections. When bacteria or viruses enter the body, they attack existing cells and then multiply. The body’s immune system uses several tools to fight off an infection. One of the most critical tools involves white or immune blood cells, which consist of macrophages, T-lymphocytes, and B-lymphocytes.

  • Macrophages are white blood cells that digest germs and dead cells. They leave behind components of the invading bacteria or virus, which are called antigens. The body recognizes antigens as dangerous and creates antibodies to target them.
  • T-lymphocytes attack cells that have already been infected.
  • B-lymphocytes produce antibodies that target the antigens left behind by macrophages.

It can take several days to mount an effective defense when your body first encounters a virus or bacteria. When it finally suppresses the infection, your body will maintain a few T-lymphocytes that can quickly go into action if the body reencounters the same pathogen. When the body detects familiar antigens, B-lymphocytes are ready to produce antibodies to attack.

How do vaccines work?

Vaccines imitate an infection to help the body develop immunity. These imitated infections will help the body to produce T-lymphocytes and antibodies. In some instances, the vaccine can trigger minor symptoms such as fever. This is a normal reaction as the body develops immunity.

When the imitation infection is gone, the body is left with a good supply of T-lymphocytes and B-lymphocytes that will recall how to fight that specific type of infection in the future.

However, it will usually take a few weeks for the body to make a sufficient number of T-lymphocytes and B-lymphocytes post-vaccination. This is why it is still possible for someone to develop an infection if they are exposed to a pathogen in the days immediately following vaccination.

Understanding types of vaccines

Contrary to many myths, vaccines are carefully developed and tested to make sure they add antigens into the body without causing illness.

Live Attenuated Vaccines: With this vaccine, a weak asymptotic form of a pathogen is introduced into the body. Since it’s weakened, the pathogen won’t spread and cause sickness. Examples include the MMR vaccine.

Inactivated Vaccines: For these vaccines, the pathogen is killed with chemicals or heat. The immune system can then use antigens to fight live versions of the virus or bacteria later. Examples include polio and rabies vaccines.

Subunit/conjugate Vaccines: For some infections, scientists isolate a specific carbohydrate or protein from the pathogen that can prompt an immune response without provoking sickness.

Examples include influenza and Human Papillomavirus (HPV) vaccines.

To make sure a vaccine is safe, scientists conduct many studies to ensure the injection will prompt an effective immune response without causing illness. This is why it can take years for vaccines to go from the lab to the doctor’s office.

In the midst of the current outbreak, researchers are working hard to expedite the development of a vaccine for the novel coronavirus that causes COVID-19.