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

Review of vaccine durability reveals only a few provide lifelong protection, highlighting factors influencing vaccine-induced immunity longevity.

Once an individual has received a measles jab, they are usually considered protected against measles disease for their entire life. The measles vaccine is one of the most potent vaccines in our armamentarium today. But this is not the case with most other vaccines. One needs to take several boosters for a long protection. Why is this the case?

We recently published a review of 34 currently licensed vaccines for the duration of their protective immunity, and found that only five vaccines provide long-lasting protection spanning more than 20 years and only three provide lifelong protection. Of these 34 vaccines, 15 provide 5-20 years of protection, whereas a similar number of other shots offer short-term protection that lasts around five years or less.

More importantly, barring a very few, most of the new-generation vaccines have a short duration of protection.

Post-vaccination immunity develops in a complex 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. In future, 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.

Following the administration of the measles and the rubella vaccines, the level of memory B cells in the blood plasma remains constant. It corresponds well with antibody levels decades later. This is not the case with the chickenpox, tetanus, and diphtheria vaccines – suggesting that memory B-cell persistence may not ensure antibody durability and that another mechanism may be involved in sustaining antibody levels.