Track topics on Twitter Track topics that are important to you
A vaccine is any preparation intended to produce immunity to a disease by stimulating the production of antibodies. It creates immunity but does not cause the disease. There are several differnt types of vaccine avalable;
Killed microorganisms; which still contain the virulant factors, so the immune system can learn to recognise them. Examples include influenza vaccine, cholera vaccine, bubonic plague vaccine, polio vaccine, hepatitis A vaccine, and rabies vaccine.
Attenuated vaccines contain live microorganisms that can no longer cause the disease, but still produce an immune response. They typically provoke more durable immunological responses and are the preferred type for healthy adults. Examples include the viral diseases yellow fever, measles, rubella, and mumps and the bacterial disease typhoid.
Toxoid vaccines are made from inactivated toxic compounds and not the whole microorganism, eg tetanus and diphtheria.
A Protein subunit of a microorganism can create an immune response, for example in Hepatitis B virus vaccine, which contains just the viral surface proteins.
Conjugate vaccines contain a mix of the bacterial coat (which needs to be recognised) and additional proteins (immunogenic), such as the haemophilus influenzae type B vaccine.
Other novel vaccine designs include dendritic cell vaccines (combining dendritic cells with antigens in order to present the antigens to the body's white blood cells), recombinant vector (a hybrid of DNA from one microorganisn and the structure of another, for complex diseases), DNA vaccination (insertion (and expression, triggering immune system recognition) of viral or bacterial DNA into human or animal cells), T-cell receptor peptide vaccines (these peptides have been shown to modulate cytokine production and improve cell mediated immunity) and the targeting of identified bacterial proteins (if involved in complement inhibition, they would neutralize the virulence mechanism). Synthetic vaccines are being developed, as are multivalent vaccines, which can act against more than one anitgen.
The success of vaccines has seen some diseases such as Polio almost eradicated. There are however, many diseases with no vaccine yet produced, althoug numerous clinical trials are underway, and early phase research into them.
Source; Adapted from WHO