Not all vaccines are the same. The way in which the body responds to a vaccine depends on the type of vaccine being administered. It is important for health professionals to understand the type of vaccines being administered and how it induces an immune response. This section includes descriptions of different types of vaccines.
Live-attenuated Vaccines
Live-attenuated vaccines induce an immune response that mimics a natural infection which often creates an effective and longer-lasting immunity. Live-attenuated vaccines use a weakened form of the infectious agent (virus or bacteria) to produce an immune response without causing illness. In general, clients who receive these vaccines can have lifetime protection after one or two doses.
Before administering live-attenuated vaccines, health professionals need to consider the following:
- Clients with immunocompromising diseases or conditions.
- Clients who take immunosuppressant agents.
- Clients for whom immunity is uncertain.
- Clients who are or may be pregnant.
Individuals with immune deficiency, such as those on immunosuppressant agents or with underlying conditions such as uncontrolled HIV, have a weakened immune system and can get very sick with live-attenuated vaccines. In general, people who are undergoing chemotherapy, who are severely immunocompromised, or who have an uncertain immune status should not receive live vaccines because of the risk of disease caused by vaccine strains. Health professionals should consult the most responsible provider before vaccination. Health professionals should refer to the Vaccination of Specific Population of the Canada Immunization Guide for specific information.
Screening Questions for Immunizing with Live Vaccines
1. Does the vaccine recipient have any immunocompromising conditions, or have they taken any medications in the past three months that cause immunosuppression, including corticosteroids?
2. If giving a live vaccine to young child (note: live vaccines are not given to infants (<12 months of age), consider:
- Is there a known or suspected family history of congenital immunodeficiency disorder, HIV infection, or a history of failure to thrive AND recurrent serious infections?
3. Has the vaccine recipient received any other live vaccines in the past four weeks?
4. Has the vaccine recipient received any transfusions of blood or blood products in the last year?
Inactivated/Killed Vaccines
Inactivated vaccines, sometimes referred to as killed vaccines, are composed of either whole or partial pathogens that are not alive and therefore cannot replicate. Pathogens become inactivated through exposure to heat, chemicals, and other purification processes. These types of vaccines prevent diseases caused by bacteria and viruses.
In this case, inactivated/killed vaccines refer to whole pathogen vaccines. Inactivated vaccines use the killed version of the pathogen and its antigens to induce an immune response. Typically, these vaccines provide immune protection that is not as effective as live-attenuated vaccines and often require multiple doses over time in order to sustain immunity as the antibody titers diminish. Generally, the first dose of an inactivated vaccine serves to prime the immune system, while protective immunity (antibody) is provided after the second or third dose. Inactivated vaccines are safer for use in immunocompromised individuals since the vaccine contains inactivated or killed pathogens.
Toxoid (inactivated toxin) Vaccines
Toxoid vaccines are used to prevent diseases caused by bacteria. The vaccine uses a toxin (rendered harmless) made by the pathogen that causes the disease. As a result, the body produces an immune response targeted to the toxin rather than the pathogen itself. It is important to note that toxins are typically responsible for symptoms of a disease, such that exposure to the toxin can elicit immunity.
Toxoid vaccines are safe because they cannot cause the disease. Toxoid vaccines typically require booster vaccinations to sustain immunity.
Subunit Vaccines: Recombinant, Polysaccharide and Conjugate Vaccines
Subunit vaccines use a piece of the pathogen, such as its protein, sugar, or capsid, to provoke an immune response. These vaccines elicit a strong and targeted response to a part of the pathogen and are typically suitable for anyone, including immunocompromised individuals. For sustained immunity, clients typically need multiple doses of vaccine.
While recombinant, polysaccharide, and conjugate are all forms of subunit inactivated vaccines, each target a particular molecular structure. Polysaccharide vaccines consist of long-chained sugar molecules attached to the surface of bacteria such as pneumococcus and meningococcus. Recombinant vaccines are genetically engineered vaccines, whereby pathogenic agents have been cloned, expressed, and purified into a vaccine.
There are several different types of vaccines available, each with a different set of properties and uses. Scientific advances and new technology will continue to change and improve the vaccine landscape. Table 1.1. offers examples of some of the vaccines associated with the various vaccine types.
Table 1.1: Vaccine Types
| Vaccine type | Vaccines |
|
Live-attenuated
|
Measles, mumps, rubella (combined vaccine) Varicella (chickenpox), Zoster (shingles) Influenza (nasal spray) Oral Polio Vaccine (OPV) Rotavirus Yellow fever
|
|
Inactivated/Killed
|
Polio (IPV) Hepatitis A Rabies
|
|
Toxoid (inactivated toxin)
|
Diphtheria Tetanus
|
|
Subunit/Conjugate
|
Hepatitis B Influenza (injection) Haemophilus influenza type b (Hib) Human papillomavirus (HPV) Pertussis Pneumococcal Meningococcal Zoster (shingles)
|
Points of Consideration
The body produces a greater immune response the more analogous the vaccine is to the original disease-causing pathogen. Live-attenuated vaccines more closely resemble their pathogen, making ongoing vaccinations less likely to achieve sustained immunity. Most live-attenuated vaccines in Canada are viral; however, there are two bacterial attenuated vaccines (typhoid and tuberculosis) that are available under special circumstances.
Attribution Statement
Content in this section was adapted, with editorial changes, from Page 8: Canadian Immunization Guide: Part 1 – Key Immunization Information by the Government of Canada and is reproduced under non-commercial conditions.
Content in Table 1.1 was adapted, with editorial changes, from https://www.vaccines.gov, which is in the public domain.
Medications that reduce or suppress the strength of a body’s immune system response (e.g., antirejection drugs following organ transplant)
Doctor or nurse practitioner
Medications that reduce inflammation
Substance that induces an immune response, trigger production of antibodies
Clinical test to measure amount of antibody in person’s blood
An additional vaccine to help sustain immunity
Capsule around the pathogen
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