Question

1. A vaccine to COVID-19 is perhaps the best way to end the pandemic. Please answer the following questions in a way that you might explain it to an intelligent patient who is asking the following questions.

a. What is a vaccine?

b. How will a vaccine help to prevent me from getting COVID-19?

c. There are more than 90 vaccines being developed against COVID-19. Three types of vaccines currently being investigated for COVID-19 are a subunit vaccine OR a RNA vaccine OR an inactivated vaccine. Choose one and explain what it is.

Answer 1

a. Vaccines mostly contain killed or weakened forms of pathogens like viruses or bacteria. They help improve body’s natural immune system by helping it recognize and fight pathogens, which then keeps us safe from the diseases they cause. Vaccines do not cause disease or other complications. They are designed to prevent the disease and not treat it. They are administered either by injection, orally or nasally.

b. Vaccines work because of the way our immune system functions. Suppose some disease-causing pathogen(COVID-19) gets in our body. Our immune system is quick to recognize them as invaders. This is because the proteins or sugars on the pathogen’s surface have different shapes to any of the ones in the human body. They trigger a complex chain of events involving many different types of white blood cells working together. Most important of these are T-lymphocytes and antibodies. Antibodies can stick to the proteins or sugars on the pathogen’s surface, and kill the pathogen or disable them. However, not all antibodies will work against these pathogens. They have to be exactly the right shape – a bit like a key fitting a lock. Our bodies have a library of white blood cells, each of which can make just one shape of antibody. Only a few of these antibodies will match the invading pathogen. Those that match, attack cells in the body that have already been infected. Once the infection goes away, our body is left with a store of memory T-lymphocytes. These memory cells develop when we get sick with a new virus so we don’t get the infection again.

Vaccines work in the same way. They contain weakened or dead bacteria or viruses, or even just a few proteins or sugars from the surface. This is enough to convince the immune system that a real invader has got in. The same process takes place as when real bacteria or viruses invade our bodies. Thus, a vaccine helps in producing memory cells and antibodies against a particular pathogen. So that if our body ever meets the real thing, our immune system will remember it and get rid of it before we even know it’s there.

c. RNA vaccine

Conventional vaccines usually contain inactivated disease causing organisms or their proteins (antigens). They stimulate the body’s immune response. Its response is more rapid and effective if exposed to the infectious agent in the future.

RNA vaccines make use of the protein making mechanism of cells . Cells use DNA as the template to make messenger RNA (mRNA) molecules which are then translated to build proteins. An RNA vaccine consists of an mRNA strand from the pathogen that codes the disease specific antigen. Once the mRNA strand in the vaccine is inside the cell, the cell uses this genetic information to produce antigen. This antigen is then displayed on the cell surface, where it is recognized by the immune system. It then treats this cell as a pathogen and produces memory cells and antibodies to kill it. Thus the immune system learns to prevent the actual disease.

Benefits:

• RNA vaccines are not made with pathogen or its particles, and are thus non-infectious.
• RNA does not integrate itself into the host genome because it degrades once the protein is made.
• RNA vaccines can be produced from a DNA template more rapidly in a process that can be standardized.

Drawbacks:

• The mRNA strand in the vaccine may produce an unintended response from the immune system.
• As free RNA in the body is quickly broken down, delivering the vaccine effectively to cells is difficult.