Live attenuated vaccines

Definition

Live attenuated vaccines are vaccines created from pathogens that have been weakened or modified so that they cannot cause disease in healthy individuals. These vaccines elicit strong immune responses by mimicking natural infections, leading to the development of immunological memory and long-lasting protection against diseases.

5 Must Know Facts For Your Next Test

1. Live attenuated vaccines often provide lifelong immunity with just one or two doses, as they stimulate a strong cellular and humoral immune response.
2. Examples of live attenuated vaccines include those for measles, mumps, rubella (MMR), and yellow fever.
3. These vaccines can replicate in the body, providing a more natural immune response, but are generally not recommended for individuals with compromised immune systems.
4. The development of live attenuated vaccines involves extensive testing to ensure that the attenuated strain does not revert to a virulent form.
5. Live attenuated vaccines can sometimes cause mild symptoms of the disease they protect against, but these are generally much less severe than the actual disease.

Review Questions

• How do live attenuated vaccines contribute to the development of immunological memory?
  • Live attenuated vaccines mimic natural infections by using weakened pathogens that can still replicate without causing disease. This replication stimulates both B cells and T cells, leading to the production of antibodies and memory cells. As a result, when the body is later exposed to the actual pathogen, the immune system can respond quickly and effectively due to this established immunological memory.
• Discuss the advantages and disadvantages of using live attenuated vaccines compared to inactivated vaccines.
  • Live attenuated vaccines have the advantage of eliciting a stronger and longer-lasting immune response with fewer doses compared to inactivated vaccines. However, they may pose risks for immunocompromised individuals since the attenuated pathogens can sometimes cause mild symptoms. In contrast, inactivated vaccines are safer for those with weakened immune systems but usually require multiple doses to achieve similar levels of immunity. Thus, the choice between them often depends on individual health factors and public health considerations.
• Evaluate the role of live attenuated vaccines in achieving herd immunity within a population.
  • Live attenuated vaccines play a critical role in achieving herd immunity by ensuring that a significant portion of the population is immune to specific infectious diseases. This immunity reduces the overall prevalence of the disease within the community, protecting those who are unvaccinated or cannot be vaccinated due to medical reasons. By maintaining high vaccination coverage through live attenuated vaccines, communities can lower transmission rates, ultimately leading to broader public health benefits and potentially eradicating certain diseases.

Related terms

Immunological memory: The ability of the immune system to remember past infections or vaccinations, enabling a quicker and more effective response upon re-exposure to the same pathogen.

Herd immunity: A form of indirect protection from infectious diseases that occurs when a large percentage of a population becomes immune, making it less likely for the disease to spread.

Inactivated vaccines: Vaccines made from pathogens that have been killed or inactivated so they can no longer replicate, typically requiring multiple doses for adequate immunity.