Written by L. M. Land
Vaccines are a modern medical miracle that have been preventing death and disability for over 80 years. Simply, vaccines work by imitating an infection to awaken the body’s natural defenses. The vast majority of the over one billion doses of vaccines manufactured worldwide each year are given to healthy babies, children and adults with little or no side effect.
Thankfully, when the COVID-19 virus began spreading around the world in 2020, there was already a large body of knowledge available about how to make vaccines. The success of the COVID vaccine is evident in our daily lives; we all have seen a drastic reduction in the number of family and friends critically ill by this virus.
Originally, there were three types of COVID-19 vaccines for use in the United States: mRNA, protein subunit and viral vector vaccines. As of May 6, 2023, J&J/Janssen COVID-19 vaccine, a viral vector vaccine, has expired and is no longer available for use in the United States.
To understand how any vaccine works, you need to understand a little about the immune system.
A pathogen is a bacterium, virus, parasite or fungus that can cause disease within the body. Each pathogen is unique. One of its many parts is an antigen.
Our bodies react to this antigen with our immune system’s ‘defense soldiers:’ antibodies. Each antibody soldier is trained to attack one specific ‘enemy’ antigen. When the human body is exposed to an antigen for the first time, it takes a few weeks for the immune system to respond and produce antibody ‘soldiers’ specific to the new antigen.
When this new antibody ‘soldier’ is created, it works with the rest of the immune system to destroy the pathogen and stop the disease. It also retains a memory of the pathogen, and every time you’re exposed, the defense system is faster to react.
If the ‘enemy antigen’ has similar cousins, like many flu viruses, the defense system will still activate. When exposed again, a person’s immune system will be able to respond immediately, protecting against disease.
This is what the vaccines do, they allow your system to have soldiers ready to act before you’ve ever been exposed. So, those who have weakened compromised immune systems are especially helped by most vaccines.
For some people after a vaccination, immunity building will cause symptoms, such as a mild fever. These are normal signs that the body is building immunity.
Because there are so many types of pathogens, there are different ways that vaccines work. A summary of each follows. The term “germs” refers to the microscopic bacteria, viruses, fungi and protozoa that can cause disease.
Inactivated vaccines
Inactivated vaccines use a dead version of the germ to create the vaccine. Therefore, they are not as strong as live vaccines. This is why several doses over time (booster shots) are needed to get full immunity. Inactivated vaccines are used to protect against hepatitis A, flu, polio and rabies.
Live-attenuated vaccines
Live vaccines use a weakened (or attenuated) form of the disease organism.
In being so similar to the original antigen, a strong and long-lasting immune response is created. Just one or two doses of most live vaccines can give you a lifetime of protection against measles, mumps, rubella, rotavirus, smallpox, chickenpox and yellow fever.
Live vaccines do have problems. Persons with weakened immune systems, organ transplants or other long-term health issues should consult with their doctor before getting this type of vaccine.
Also, the vaccines must be kept cool, and cannot be used in locations without refrigerators.
Messenger RNA vaccines—also called mRNA vaccines
The current COVID-19 vaccines are this type. These vaccines make proteins to create an immune response in the body. They do not contain a live virus. There is no risk of getting COVID-19 from the vaccine.
Another benefit of an mRNA vaccine is a shorter manufacturing time, which was beneficial when our planet was shut down in 2020.
Currently, Pfizer and Moderna are manufacturing bivalent mRNA vaccines for COVID-19. Bivalent is a term meaning they were updated to protect against two virus strains: the original one and the BA.4/BA.5 Omicron subvariants.
Subunit, recombinant, polysaccharide, and conjugate vaccines
Subunit, recombinant, polysaccharide, and conjugate vaccines use specific parts of the germ—like its protein, sugar or capsid (a casing around the germ).
Because these vaccines use parts of the germ, they give a very strong immune response. They are safe to use on almost everyone, including people with weakened immune systems and long-term health problems. You may need boosters to maintain protection.
These vaccines are used to protect against: Hib (Haemophilus influenzae type b) disease, HPV (Human papillomavirus, whooping cough (part of the DTaP combined vaccine), pneumococcal disease, meningococcal disease and shingles.
Toxoid vaccines
Toxoid vaccines use a toxin made by the disease itself. They create immunity to the individual parts of a germ that cause a disease instead of the germ itself. That means the immune response is targeted to the toxin instead of the whole germ. Booster shots may be needed. The diseases treated with toxoid vaccines are diphtheria and tetanus.
Viral vector vaccines
Viral vector vaccines use a modified version of a different virus as a substitute, or vector, to deliver protection. Several different viruses have been used as vectors, including influenza, vesicular stomatitis virus (VSV), measles virus and adenovirus (the common cold). Viral vector vaccines are used to protect against COVID-19, and studies are focusing on the use of viral vector vaccines for Zika, flu and HIV. It has also been used for Ebola vaccines.
Are Vaccines Safe? Yes, for most people. There are always exceptions to the rules, like allergy to a vaccine ingredient or risks for the immunocompromised with live vaccines. These are rare.
Can you still get infected after vaccination?
Because immunity can take weeks to develop after vaccination, it is possible to become infected in the weeks immediately following vaccination. Even after that, vaccinated people can and sometimes do get infected, which has been seen with COVID in particular in the last year. But a vaccinated person is far less likely to die or become seriously ill than someone whose immune system is unprepared to fight an infection.
Sources:
https://www.cdc.gov/vaccines/hcp/vis/index.html
https://www.hhs.gov/immunization/basics/types/index.html
https://www.cdc.gov/vaccines/hcp/conversations/understanding-vacc-work.html
https://www.who.int/news-room/feature-stories/detail/how-do-vaccines-work
https://www.hhs.gov/immunization/basics/types/index.html