Attenuated vaccines typically cause a stronger immune response because
they are given to people with a weakened immune system.
the pathogens used in these vaccines are extremely virulent.
large numbers of pathogens are used in them.
they are given to people who have a very strong immune system.
the pathogen can still multiply in the host.
The correct answer and explanation is :
The correct answer is: the pathogen can still multiply in the host.
Explanation:
Attenuated vaccines, also known as live-attenuated vaccines, use a version of the living pathogen that has been weakened in the laboratory. Although the pathogen is weakened so it does not cause disease in healthy individuals, it is still alive and capable of limited replication in the body. This ability to replicate — even at a low level — is what helps stimulate a stronger and longer-lasting immune response compared to vaccines made with killed (inactivated) pathogens or isolated parts of the pathogen.
When the attenuated pathogen enters the host, it behaves similarly to a natural infection but without causing full-blown illness. As the weakened pathogen multiplies, it triggers the immune system to respond as if it were encountering the real infection. This includes activating both the humoral immune response (production of antibodies by B cells) and the cell-mediated immune response (activation of T cells). These multiple layers of immune activation often result in stronger immunity and longer-lasting protection, sometimes even for life with just one or two doses.
It is important to note that attenuated vaccines are generally not given to people with weakened immune systems (such as those with HIV/AIDS, cancer patients receiving chemotherapy, or organ transplant recipients) because even a weakened pathogen could potentially cause serious illness in those individuals. This rules out the choices about giving them to people with weak or strong immune systems as the reason for a stronger immune response.
Examples of live-attenuated vaccines include:
- Measles, Mumps, and Rubella (MMR) vaccine
- Varicella (chickenpox) vaccine
- Yellow fever vaccine
In short, because the pathogen in attenuated vaccines can still multiply to a limited degree, the immune system gets a more “realistic” practice run, leading to strong, effective, and long-term immunity.