Vaccine

A vaccine is a biological preparation that provides active acquired immunity tae a parteecular disease. A vaccine teepically contains an agent that resembles a disease-causin microorganism an is eften made frae weakened or killed forms o the microbe, its toxins, or ane o its surface proteins. The agent stimulates the body's immune seestem tae recognise the agent as a threat, destroy it, an tae further recognise an destroy ony o the microorganisms associated wi that agent that it mey encounter in the future. Vaccines can be prophylactic (ensaumple: tae prevent or ameliorate the effects o a future infection bi a naitural or "wild" pathogen), or therapeutic (e.g., vaccines against cancer are bein investigated).

The admeenistration o vaccines is cried vaccination. Vaccination is the maist effective method o preventin infectious diseases; widespread immunity due tae vaccination is largely responsible for the warldwide eradication o smallpox an the restriction o diseases sic as polio, maisles, an tetanus frae much o the warld.

The effectiveness o vaccination haes been widely studied an verified; for ensaumple, the influenza vaccine, the HPV vaccine, an the chicken pox vaccine. The Warld Health Organization (WHO) reports that licensed vaccines are currently available for twinty-five different preventable infections.

The terms vaccine an vaccination are derived frae Variolae vaccinae (smallpox o the cow), the term devised bi Edward Jenner tae denote cowpox. He uised it in 1798 in the lang title o his Inquiry into the Variolae vaccinae known as the Cow Pox, in which he describit the protective effect o cowpox against smallpox. In 1881, tae honour Jenner, Louis Pasteur proposed that the terms should be extendit tae kiver the new protective inoculations then bein developed.

Effectiveness

Vaccines hae historically been the maist effective means tae fecht an eradicate infectious diseases. Limitations tae thair effectiveness, nevertheless, exist. Whiles, pertection fails acause the host's immune seestem simply daes nae respond adequately or at aw. Lack o response commonly results frae clinical factors sic as diabetes, steroid uise, HIV infection or age.^{[citation needit]} It an aa might fail for genetic reasons if the host's immune seestem includes no strains o B cells that can generate antibodies suited tae reacting effectively an binding tae the antigens associated wi the pathogen.^{[citation needit]}