A vaccine is a pharmacological preparation, which can be administered parenterally or orally, which allows to create an "immunization against one or more specific pathogenic microorganisms (N.B: the most common pathogenic microorganisms are viruses and bacteria).
Vaccines may contain an attenuated form of the pathogen against which immunization is desired, or they may contain proteins or toxins deriving from this same pathogen.
There are three major types of vaccines:
- Live attenuated vaccines. They contain the microorganisms against which immunization is to be obtained in a live form, but with a reduced pathogenic power.
- Inactivated vaccines. They contain a complete but dead (therefore inactive) form of the microorganisms against which immunization is desired.
- Vaccines with purified antigens. They contain, in inactivated form, proteins, toxins or polysaccharides of the microorganism against which the recipient individual is to be immunized.
Vaccines act by activating the immune system: once administered, in fact, they stimulate the so-called B lymphocytes (a class of immune system cells) to produce antibodies, which are the real architects of immunization.
Vaccines do not have an immediate effect: the antibody response, in fact, requires a period of time ranging from 2 to 4 weeks.
and anti-tetanus, vaccines that are clearly not dangerous for the pregnant woman and the fetus.
, which affects the upper and sometimes lower respiratory tracts.
Transmissible both directly (cough, sneezing, etc.) and indirectly (contact with contaminated objects), influenza typically manifests itself with symptoms such as fever, cough, sneezing, runny nose, general malaise and myalgia (muscle pain) .
The cause of the flu is a virus from the family of Orthomyxoviridae very particular: this virus, in fact, changes its external structure (the so-called capsid) within a few months, thus always being different; this singular behavior is the main reason why flu vaccination needs to be renewed every year.
Influenza is generally an infectious disease with a benign course (healing usually occurs within 6 days); however, in people with chronic diseases and in general in all those with weaker immune defenses (therefore children and the elderly), it can turn out to be a very dangerous infection, also capable of causing bronchitis, pneumonia or bronchopneumonia with serious consequences.
