Live attenuated vaccines

Definition

Live attenuated vaccines are vaccines that use a weakened form of the pathogen that causes a disease, which stimulates an immune response without causing the disease itself. These vaccines can provide strong and long-lasting immunity by mimicking a natural infection, often resulting in both humoral and cell-mediated immunity. They are particularly effective against viral infections, especially those caused by enveloped viruses, but may have limitations regarding stability and storage.

5 Must Know Facts For Your Next Test

1. Live attenuated vaccines are often derived from wild-type pathogens that are modified to lose their virulence while still being able to replicate in the host.
2. These vaccines tend to require fewer doses compared to inactivated vaccines because they induce a more robust and longer-lasting immune response.
3. Storage and handling of live attenuated vaccines can be challenging, as they often require refrigeration to maintain their efficacy.
4. Examples of live attenuated vaccines include those for measles, mumps, rubella (MMR), and yellow fever.
5. Because live attenuated vaccines contain weakened pathogens, there is a small risk of causing mild illness in immunocompromised individuals.

Review Questions

• How do live attenuated vaccines stimulate an immune response compared to inactivated vaccines?
  • Live attenuated vaccines stimulate an immune response by using a weakened form of the pathogen that can replicate without causing disease. This mimics a natural infection, activating both the humoral and cell-mediated immune responses, often leading to long-lasting immunity. In contrast, inactivated vaccines use killed pathogens that do not replicate, usually resulting in a weaker immune response and requiring multiple doses for effective immunity.
• Discuss the advantages and challenges associated with using live attenuated vaccines in public health strategies.
  • Live attenuated vaccines offer significant advantages such as strong and long-lasting immunity after fewer doses, making them efficient for mass vaccination campaigns. However, challenges include their storage requirements, as many must be kept refrigerated to remain effective. There is also a risk for immunocompromised individuals who may experience mild symptoms due to the weakened pathogen, necessitating careful consideration in public health strategies.
• Evaluate the role of live attenuated vaccines in achieving herd immunity and its implications for viral outbreaks.
  • Live attenuated vaccines play a critical role in achieving herd immunity by effectively immunizing individuals against highly contagious viral diseases. When a large portion of the population is vaccinated, it reduces overall transmission rates, protecting even those who are unvaccinated or immunocompromised. This collective immunity significantly lowers the likelihood of outbreaks and protects vulnerable populations, demonstrating the importance of widespread vaccination programs in controlling viral infections.

Related terms

Immunogenicity:

The ability of a vaccine to provoke an immune response in the body, leading to the production of antibodies and memory cells.

Herd immunity: A form of indirect protection from infectious diseases that occurs when a large percentage of a population becomes immune, reducing the spread of the disease.

Inactivated vaccines: Vaccines that use killed or inactivated pathogens to stimulate an immune response without causing disease, generally requiring multiple doses for full immunity.