Define vaccine.

Hint:- it is a type of an acquired immunity. A biological preparation that increases one’s resistance power towards a particular infectious disease. The term is derived from Variolae vaccinae.

Complete Answer:-A biological preparation that contains a dead or weakened version of a microbe. Vaccine helps your immune system recognize and destroy the living microbe during a future infection.The agent stimulates the body's immune system to recognize the agent as a threat and destroy it.A vaccine can be of two types:
- Prophylactic
- Therapeutic
Its administration into the body is known as vaccination. it is the most effective method of preventing infectious diseases. After vaccination the body recognizes the protein coat on the virus, and thus is prepared to respond, by first neutralizing the target agent before it can enter cells, and secondly by recognizing and destroying infected cells before that agent can multiply to vast numbers.
Vaccine production has several stages.
In the first stage, the antigen itself is generated. To obtain antigen the viruses are grown either on primary cells such as chicken eggs (e.g., for influenza) or on continuous cell lines such as cultured human cells (e.g., for hepatitis A).
In the second stage after the antigen is generated, it is isolated from the cells used to generate it. After that virus may need to be inactivated, possibly with no further purification required.
Finally, the vaccine is formulated by adding adjuvant, stabilizers, and preservatives as needed.
The final stage in vaccines is the process of filling vials with vaccines and packaging them for distribution.

Note:- Widespread immunity due to vaccination is largely responsible for the worldwide eradication of smallpox and the restriction of diseases such as polio, measles, and tetanus.
However, not all can take vaccines. Infants which are around 2 months as well as people who are under certain medications are advised not to take vaccines.