Which of the following statements is true regarding vaccines?
A.
Vaccines can cause the disease they are designed to protect against
B.
Vaccines work by providing passive immunity to the individual
C.
Vaccines work by exposing the individual to a weakened or inactivated form of the pathogen
D.
Vaccines only provide protection against bacterial infections
The correct answer and Explanation is :
The correct answer is:
C. Vaccines work by exposing the individual to a weakened or inactivated form of the pathogen.
Explanation:
Vaccines are designed to protect individuals from infectious diseases by stimulating the immune system to recognize and combat specific pathogens. They achieve this through a process called immunization. Here’s how this works:
- Types of Vaccines: Vaccines contain antigens, which are substances that provoke an immune response. These antigens can be in the form of weakened (live attenuated) or inactivated (killed) pathogens, or parts of the pathogen like proteins or sugars. For example:
- Live attenuated vaccines: These contain a version of the living pathogen that has been weakened so it cannot cause disease. Examples include the measles, mumps, and rubella (MMR) vaccine.
- Inactivated vaccines: These contain pathogens that have been killed or inactivated so they can no longer cause disease. Examples include the polio vaccine.
- Subunit, recombinant, or conjugate vaccines: These include pieces of the pathogen, such as proteins, rather than the whole pathogen. Examples include the human papillomavirus (HPV) vaccine and the Haemophilus influenzae type b (Hib) vaccine.
- Immune Response: When a vaccine is administered, the immune system recognizes the antigens as foreign. This exposure leads to the production of antibodies and the activation of T-cells that specifically target the pathogen. This process mimics what happens during an actual infection but without causing the disease itself.
- Memory: The immune system develops a memory of the pathogen, which allows it to respond more rapidly and effectively if exposed to the actual pathogen in the future. This means the person is protected from getting sick from the disease that the vaccine targets.
Why the Other Statements Are Incorrect:
- A. Vaccines can cause the disease they are designed to protect against: This is generally false. Most vaccines are designed to be safe and do not cause the disease they protect against. Live attenuated vaccines might cause mild symptoms similar to the disease, but they are not the same as getting the full-blown disease.
- B. Vaccines work by providing passive immunity to the individual: This is incorrect. Vaccines provide active immunity, not passive. Passive immunity is provided by transferring antibodies from another source, such as through maternal antibodies or antibody injections.
- D. Vaccines only provide protection against bacterial infections: This is false. Vaccines can protect against both bacterial and viral infections. For example, vaccines are available for diseases caused by bacteria (like tuberculosis and whooping cough) and viruses (like influenza and hepatitis).