Why do vaccines work?

As a child, we dont pay much mind to what the unusual substance in needles that get injected in us are really for. We just sit tight, squeeze our parents hand with tears in our eyes- in hopes for the procedure to be over as soon as possible. Well now, we shall find out; what consisted in that tiny needle was possibly what has kept us alive today.

What are in vaccines?

Simply put, a vaccine consists of a dead version of a pathogen ( a microorganism which causes disease).

Different vaccines have their specific dead pathogen in them, eg: small pox vaccines consist of the dead pathogen that causes small pox. This is because a vaccine consisting of the live pathogen would end up giving the person the disease, so killing the pathogen only stimulates the immune response with no harmful symptoms.

Vaccination — OCR A Level Biology Revision Notes

How the body reacts to the vaccine

The dead pathogen in a vaccine consists of antigens, which are also protiens or glycoprotiens that stimulate an immune response.

The antigen is recognised as “foreign” to the body and thus the humoral response takes place. A naive B-cell internalises the pathogen and releases the antigens on its cell surface membrane (now an antigen presenting cell-APC). A T helper cell with a complementary receptor to the antigen on the B-cell then binds to it (clonal selection). The T helper cell then releases interleukins which stimulate mitosis for the B-cell ( clonal expansion). The B-cell then differentiates into memory B-cells and plasma B-cells. The plasma B-cell is able to produce and release antibodies specific to the antigen of the pathogen, which then bind to the pathogen by either acting as :

Opsonins: binding to the pathogen to encourage phagocytosis

Agglutinins: clump up the pathogen for easy pagocytosis

Antitoxins: neutralise the toxins

Ultimately allowing phagocytosis to occur which diminishes and destroys the pathogen from the body.

Thank you for reading!

Sonakshi saha