Post-Vaccination Immunity

About Post-vaccination immunity

• It develops in a complex process.
• Process
  • In the fundamental immunological mechanism, our lymph nodes first produce the memory B cells that confer long-term protection against a disease.
  • These cells ‘memorise’ the antigen the vaccine has delivered.
  • When a foreign object like a virus enters the body bearing the same antigen, the B cells will trigger the production of a large number of potent antibodies to destroy it, removing the infection.
  • These memory B cells require T cell support, and only vaccines that stimulate T cells can also induce the body to produce them. Further, not all vaccines – including the polysaccharide typhoid and the pneumococcal vaccines – prompt the body to make B cells.
  • In some cases, frequent boosters are required to enhance the duration of immunity the cells confer, ranging from six months to a few years.
  • Also, vaccines trigger the production of memory B cells to different degrees, plus having memory B cells alone does not guarantee protection.
• Another essential immune cell, called long-lasting plasma cell (LLPC), migrates from the lymph node to the bone marrow and may endure for decades.
• LLPCs are the main immunological factor in vaccine-induced immunity. Every vaccine tries to create long-lasting plasma cells for lifelong protection.
• The measles and rubella vaccines produce these cells in the bone marrow. However, some potent vaccines, such as the mRNA COVID-19 shots, fail to activate these cells in the bone marrow. 
• To provide long-term protection, then, vaccines must generate memory B cells and LLPCs in the bone marrow. Different vaccines differ in their ability to produce these cells, explaining the disparity in their durabilities.

Q1) What are Lymph nodes?

A small bean-shaped structure that is part of the body’s immune system. Lymph nodes filter substances that travel through the lymphatic fluid, and they contain lymphocytes (white blood cells) that help the body fight infection and disease. There are hundreds of lymph nodes found throughout the body. 

Source: Why do so many contemporary vaccines have low durability? | Explained