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. H. influenzae polysaccharide bound to diphtheria toxoid
g. a plasmid containing genes for influenza A protein

Verified step by step guidance

1. Identify the type of each vaccine: a. Attenuated measles virus is a live attenuated vaccine. b. Dead Rickettsia prowazekii is an inactivated (killed) vaccine. c. Vibrio cholerae toxoid is a toxoid vaccine. d. Hepatitis B antigen produced in yeast cells is a subunit vaccine. e. Purified polysaccharides from Streptococcus pyogenes is a polysaccharide vaccine. f. H. influenzae polysaccharide bound to diphtheria toxoid is a conjugate vaccine. g. A plasmid containing genes for influenza A protein is a DNA vaccine.
2. Determine which vaccine types could potentially cause the disease they are meant to prevent: Live attenuated vaccines, like the attenuated measles virus, have a small risk of causing disease, especially in immunocompromised individuals, because they contain a weakened form of the pathogen.
3. Understand the mechanism of each vaccine type: Live attenuated vaccines use a weakened form of the germ. Inactivated vaccines use a killed version of the germ. Toxoid vaccines use a toxin made by the germ. Subunit vaccines use specific pieces of the germ. Polysaccharide vaccines use long chains of sugar molecules that make up the surface capsule of certain bacteria. Conjugate vaccines link polysaccharides to a protein to improve immune response. DNA vaccines use genetic material to induce an immune response.
4. Consider the safety profile of each vaccine type: Inactivated, toxoid, subunit, polysaccharide, conjugate, and DNA vaccines generally do not cause the disease they are designed to prevent because they do not contain live pathogens.
5. Summarize the findings: The attenuated measles virus vaccine is the only one among the listed vaccines that could potentially cause the disease it is supposed to prevent, due to its live attenuated nature.

Key Concepts

Types of Vaccines

Vaccines can be classified into several types based on their composition and mechanism of action. The main categories include live attenuated vaccines, inactivated (or killed) vaccines, subunit vaccines, and toxoid vaccines. Live attenuated vaccines contain weakened forms of the pathogen, while inactivated vaccines contain killed pathogens. Subunit vaccines include only parts of the pathogen, and toxoid vaccines contain inactivated toxins.

Live Attenuated Vaccines

Live attenuated vaccines use a weakened form of the pathogen that can still replicate but does not cause disease in healthy individuals. These vaccines often provide strong and long-lasting immunity, as they closely mimic a natural infection. However, there is a small risk that they could cause disease in immunocompromised individuals or if the vaccine reverts to a virulent form.

Inactivated and Subunit Vaccines

Inactivated vaccines contain pathogens that have been killed or inactivated, making them unable to cause disease. Subunit vaccines, on the other hand, consist of specific pieces of the pathogen, such as proteins or sugars, which stimulate an immune response without the risk of disease. Both types generally require multiple doses to achieve effective immunity and may not provide as robust a response as live attenuated vaccines.