When the vaccine is injected, the agent goes into the cells of our tissues. Thereafter, it captures the attention of certain ‘dendritic’ cells, which have a specific function to monitor intruders that might have entered the body. The patrolling cells notice this never before seen agent and alarm the body against it.
The dendritic cells do this by reading the genetic instructions about the virus injected into the body through the vaccine. Thereafter, the information is replicated for the immune system to read and react.