Question

Classify the following vaccines by type. Which could cause the disease it is supposed to prevent? a. attenuated measles virus b. dead Rickettsia prowazekii c. Vibrio cholerae toxoid d. hepatitis B antigen produced in yeast cells e. purified polysaccharides from Streptococcus pyogenes f. Haemophilus influenzae polysaccharide bound to diphtheria toxoid g. a plasmid containing genes for influenza A protein

Short answer

The attenuated measles virus could potentially cause the disease it is meant to prevent.

Step-by-step solution

Identify the Types of Vaccines

To classify the vaccines listed, first understand the types of vaccines: 1) Attenuated (live) vaccines contain live but weakened versions of the virus or bacteria. 2) Inactivated (killed) vaccines contain dead pathogens. 3) Toxoid vaccines contain inactivated toxins. 4) Subunit, recombinant, polysaccharide, and conjugate vaccines contain specific pieces of the germ. 5) DNA vaccines use engineered DNA to induce an immune response.

Classify Each Vaccine

- **a. attenuated measles virus**: This is a live attenuated vaccine. - **b. dead Rickettsia prowazekii**: This is an inactivated vaccine. - **c. Vibrio cholerae toxoid**: This is a toxoid vaccine. - **d. hepatitis B antigen produced in yeast cells**: This is a recombinant vaccine. - **e. purified polysaccharides from Streptococcus pyogenes**: This is a polysaccharide vaccine. - **f. Haemophilus influenzae polysaccharide bound to diphtheria toxoid**: This is a conjugate vaccine. - **g. a plasmid containing genes for influenza A protein**: This is a DNA vaccine.

Identify Vaccines That Could Cause the Disease

Vaccines that use live attenuated pathogens have a theoretical risk of causing the disease in people with weakened immune systems. Thus, the **attenuated measles virus** vaccine could potentially cause illness in such individuals.

Key concepts

Attenuated Vaccines

Attenuated vaccines are composed of live but weakened strains of the virus or bacteria they are designed to protect against.
They work by simulating a natural infection, which helps the immune system to develop a strong and lasting response.
Since the pathogens are still "alive," the body learns how to fight them effectively. - **How they work:** These vaccines mimic a real infection, thus stimulating a comprehensive immune response. - **Examples:** Measles, mumps, rubella (MMR), and live attenuated influenza vaccines. One notable advantage of attenuated vaccines is their ability to induce long-lasting immunity with often only one or two doses.
However, because they contain live organisms, there is a slightly higher risk for individuals with weakened immune systems, who might develop the disease.
This rare occurrence makes it crucial to ensure that such vaccines are administered appropriately.

Inactivated Vaccines

Inactivated vaccines use a killed version of the pathogen to provoke an immune response without risking disease in the recipient.
This type of vaccine is considered very safe because the pathogen is dead and cannot cause illness. - **How they work:** When injected, the immune system encounters the dead germs and builds a defense against them. - **Examples:** Polio, hepatitis A, and rabies vaccines. Inactivated vaccines generally require multiple doses over time (boosters) to maintain immunity, since they don't mimic an infection as closely as live vaccines.
The main benefit of inactivated vaccines is their safety profile, making them suitable for people with weakened immune systems.

Toxoid Vaccines

Toxoid vaccines contain inactivated toxins (toxoids) produced by certain bacteria, which can cause disease. These vaccines do not target the bacteria directly but instead neutralize the toxins they release. - **How they work:** They contain a modified toxin that cannot cause illness but can stimulate the immune system to mount a defense. - **Examples:** Tetanus and diphtheria vaccines. Toxoid vaccines are highly effective for diseases where the bacteria produce toxins they need to survive.
These vaccines are often included in a combination that targets multiple diseases at once.

Recombinant Vaccines

Recombinant vaccines involve the introduction of a piece of the virus's or bacteria's genetic material into another cell, often yeast or bacterial, to produce an immune-provoking antigen. The antigen is then purified and used in the vaccine. - **How they work:** The body's immune system recognizes this antigen as foreign and mounts a defense against it. - **Examples:** Hepatitis B and human papillomavirus (HPV) vaccines. Recombinant vaccines are safe because they do not contain the pathogen itself, only the antigen to which the immune system reacts.
They offer a high level of safety and are effective across a wide range of population groups, including those with compromised immune systems.

DNA Vaccines

DNA vaccines are a newer type of vaccine using genetically engineered DNA to produce an immune response. These vaccines introduce a specific gene or DNA sequence into the body, prompting cells to produce an antigen associated with the pathogen. - **How they work:** Once inside the body, the cells read the DNA and produce the antigen, triggering an immune response. - **Advantages:** They are relatively easy to produce and can be quickly adapted to target new pathogens. Though still in the developmental phase for many diseases, the potential for DNA vaccines is vast due to their stability and ease of delivery.
These vaccines can potentially offer longer-lasting immunity with fewer doses.