Sarah Bennett
Vaccines are a powerful tool to protect oneself from serious diseases. They work by imitating an infection, triggering the body's natural defences, and teaching the immune system to fight off certain types of germs and the diseases they cause. There are several types of vaccines, including inactivated vaccines, live vaccines, toxoid vaccines, and viral vector vaccines. Inactivated vaccines use a killed version of the germ, while live vaccines use a weakened form. Toxoid vaccines target the harmful products made by germs, and viral vector vaccines use specific pieces of the germ to trigger a strong immune response. The immune system has two main subsystems: the innate immune system and the adaptive immune system, which work together to provide an effective immune response. Vaccines induce both subsystems to create long-term immunity. The innate immune system acts as a first line of defence, while the adaptive immune system produces antibodies, which are proteins that neutralise or destroy toxins or disease-causing organisms. Antibodies are disease-specific, and active immunity takes time to develop but can last longer than passive immunity. Passive immunity is provided by antibodies from another person or animal and offers immediate but short-lived protection.
| Characteristics | Values |
|---|---|
| Type of immunity | Active and passive |
| Active immunity | Results when exposure to a disease organism triggers the immune system to produce antibodies to that disease |
| Passive immunity | Results when a person is given someone else's antibodies |
| Active immunity duration | Long-lasting, sometimes life-long |
| Passive immunity duration | Short-lived, fades within weeks or months |
| Active immunity development time | Slow |
| Passive immunity development time | Immediate |
| Active immunity example | MMR (measles, mumps, and rubella) combined vaccine |
| Passive immunity example | Antibodies given as medication |
| Active immunity advantages | Long-lasting protection |
| Passive immunity advantages | Immediate protection |
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What You'll Learn
Active vs. passive immunity
Vaccination is one of the best ways to protect yourself from serious diseases. Vaccines work by imitating an infection to engage the body's natural defences. They help the body learn how to defend itself from disease without the dangers of a full-blown infection.
There are two types of immunity: active and passive. Active immunity occurs when exposure to a disease organism triggers the immune system to produce antibodies to that disease. This can occur naturally when a person is infected by a pathogen, or through vaccination. Vaccines introduce a killed or impaired version of a pathogen or a subunit of it into the body, giving the immune system a safe way to create an immune response.
Passive immunity, on the other hand, occurs when a person is given antibodies to a disease rather than producing them through their own immune system. Passive immunity can be provided by antibodies created outside of the individual’s body, such as those passed from a mother to her baby during pregnancy and breastfeeding. It can also be acquired through antibody-containing blood products, such as immune globulin, or through the infusion of convalescent plasma or monoclonal antibodies. The major advantage of passive immunity is that protection is immediate, whereas active immunity takes time to develop (usually several weeks). However, passive immunity typically only lasts a few weeks or months, while active immunity is long-lasting and can sometimes be lifelong.
An important phenomenon to consider when discussing active and passive immunity is immune blunting. This occurs when passive immunity interferes with the body's ability to produce its own antibodies in response to vaccination or infection. For example, circulating maternal anti-measles virus antibodies can prevent an infant’s B cells from producing its own antibodies in response to a measles vaccination.
In summary, active and passive immunity both contribute to a well-equipped and strong immune system. Active immunity takes longer to develop but lasts longer, while passive immunity provides immediate protection that fades more quickly.
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Live vs. non-live vaccines
Vaccines work by imitating an infection to engage the body's natural defences. They help the body learn how to defend itself from disease without the dangers of a full-blown infection. There are several types of vaccines, including inactivated vaccines, live vaccines, mRNA vaccines, toxoid vaccines, and subunit vaccines.
Inactivated Vaccines
Inactivated vaccines use a killed version of the germ that causes a disease. While they usually don't provide immunity that is as strong as live vaccines, they can still create an immune response without causing the disease. Multiple doses are often needed to build up immunity and offer full protection.
Live Vaccines
Live vaccines, also known as live-attenuated vaccines, use a weakened form of the germ that causes a disease. They create a strong and long-lasting immune response because they are very similar to the natural infection they help prevent. Just one or two doses of most live vaccines can provide a lifetime of protection. However, live vaccines have some limitations. For example, people with weakened immune systems or long-term health problems should consult their healthcare provider before receiving a live vaccine. Additionally, live vaccines need to be kept cool, limiting their use in certain regions.
MRNA Vaccines
MRNA vaccines do not contain a live virus, so there is no risk of causing disease in the person receiving the vaccine. They have shorter manufacturing times compared to other types of vaccines.
Toxoid Vaccines
Toxoid vaccines use inactivated toxins to target the toxic activity of bacteria, rather than the bacteria itself. They are effective in preventing certain toxin-mediated diseases such as tetanus, diphtheria, and pertussis.
Subunit Vaccines
Subunit vaccines, also known as conjugate or recombinant vaccines, are made from pieces of a pathogen rather than the whole organism. They do not contain any live pathogens, so they cannot cause sickness or infection. This makes them suitable for people who cannot receive live vaccines, such as young children, older people, and immunocompromised individuals.
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Toxoid vaccines
Vaccines are designed to teach the immune system how to fight off certain types of germs and the diseases they cause. There are several types of vaccines, including inactivated vaccines, live vaccines, and toxoid vaccines.
Diphtheria toxoid, for instance, is prepared by treating the toxin with formaldehyde and is standardized according to the specifications of the US Food and Drug Administration. Pediatric preparations of diphtheria toxoids contain 6.7 Lf units or more of diphtheria toxoid per 0.5 mL dose, while adolescent and adult preparations contain no more than 2 Lf units of toxoid per 0.5 mL dose. Tetanus toxoid is another commonly used toxoid, derived from Clostridium tetani.
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mRNA vaccines
Vaccines are designed to teach the immune system how to fight certain germs and the diseases they cause. There are several types of vaccines, including inactivated vaccines, live vaccines, toxoid vaccines, and viral vector vaccines.
Currently, the only mRNA vaccines available are for COVID-19, including Comirnaty (Pfizer-BioNTech) and Spikevax (Moderna). Scientists are investigating other ways to use mRNA technology in vaccines for other infectious diseases and cancer.
Overall, mRNA vaccines are a promising new type of vaccine that offers several advantages over traditional vaccines. By training the body to recognize and fight harmful pathogens, mRNA vaccines provide protection against infectious diseases.
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Antibody production
Vaccines are designed to teach the immune system to fight off certain types of germs and the diseases they cause. They work by imitating an infection to engage the body's natural defences. The active ingredient in all vaccines is an antigen, which causes the immune system to begin producing antibodies.
Antibodies are proteins produced by white blood cells to identify and neutralise foreign substances. White blood cells are created in the bone marrow and are dispersed throughout the body in low numbers, ready to multiply and attack microbes and other foreign substances. Once an infection is eliminated, white blood cells stop multiplying and their numbers decrease, leaving only a few to keep watch. At this point, a person is considered immunised.
Vaccines induce immunity by introducing a killed or weakened form of the disease-causing organism. If an immunised person comes into contact with the disease in the future, their immune system will recognise it and immediately produce the antibodies needed to fight it.
After vaccination, B lymphocytes detect the antigens in the vaccine and react as if the real infectious organism was invading the body. The B lymphocytes multiply to form identical cells that can respond to the antigens in the vaccine. These cloned cells then evolve into plasma cells, which produce antibodies trained to attach to and inactivate the organism the vaccine is targeting.
The body continues making antibodies and memory B cells for a few weeks after vaccination. Over time, the antibodies disappear, but the memory B cells remain dormant in the body for years. These memory B cells keep a memory of the organism the body was vaccinated against. If exposed to the organism again, the dormant memory cells will recognise it and rapidly multiply, developing into plasma cells. The plasma cells are already trained to produce antibodies against the organism, so they are able to produce a large number of antibodies very quickly, within hours. These antibodies attach to the invading organisms and prevent them from attacking healthy cells. This accelerated and more intense immune response generated by the memory B cells is known as the secondary response.
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Frequently asked questions
Vaccines provide active immunity, which results when exposure to a disease organism triggers the immune system to produce antibodies to that disease.
Active immunity is induced by vaccines that contain weakened or inactive parts of a particular disease-causing organism (antigen) that triggers an immune response within the body.
Active immunity takes several weeks to develop. During this time, an individual remains susceptible to infection.
Active immunity is long-lasting and sometimes life-long.
Passive immunity is a different type of immunity that results when a person is given someone else's antibodies.
