More about flu vaccines

What are vaccines and toxoids?

When you are exposed to a live virus in nature, your body tries to fight it by building antibodies. If your body is successful, you develop immunity much as if you have been vaccinated. If your body is not successful, you contract the disease (become symptomatic).

Immunity can be acquired naturally or artificially. In either case, the host is exposed to an antigen (foreign protein), the antigen is recognized, and the host builds a complex immune response to neutralize the antigen.

Vaccines artificially expose the host to antigens which then elicit an immune response. There are two types of vaccines: killed vaccines and modified live [attenuated] vaccines (MLV). Killed vaccines are composed of agent antigens but not living agent. Modified live vaccines are composed of non-virulent, living strains of the agent [virus or antivirulent bacteria].

Toxoids are harmless derivatives of microbiologic toxins that simulate an active immune response to toxins released by pathogens and other poisonous sources (i.e., tetanus toxoid). (http://www.sjsu.edu/faculty/gerstman/hs161/hint-vaccines.htm)

Modified live (attenuated) vaccines (MLV) are quicker acting and more immediately effective.

Killed vaccines may be killed viruses, killed bacteria called bacterins, or killed toxins called toxoids that were created and killed by either heat or chemicals.

In killed vaccines an adjuvant is added to the solution of killed organisms to help it stimulate the immune system. Dead virus or bacteria are not as easily recognized by the immune system without an adjuvant. The adjuvant also holds the killed organisms at the injection site. This allows time for the immune cells to respond to it. (http://www.productionvalues.com/ProductionValues/vaccine_basics/vaccine_basics.html)

…[A]ntibodies made in response to vaccination with one strain of influenza viruses can provide protection against different, but related strains. A less than ideal match may result in reduced vaccine effectiveness against the variant viruses, but it still can provide enough protection to prevent or lessen illness severity and prevent flu-related complications. In addition, it’s important to remember that the influenza vaccine contains three virus strains so the vaccine can also protect against the other two viruses. For these reasons, even during seasons when there is a less than ideal match, CDC continues to recommend influenza vaccination. This is particularly important for people at high risk for serious flu complications and their close contacts. (http://www.cdc.gov/flu/about/qa/season.htm)

How are these vaccines made and who decides which strains to put in the yearly flu vaccine? 

Each year, three strains are chosen for selection in that year’s flu vaccination by the WHO http://en.wikipedia.org/wiki/National_Influenza_Centers”>Global Influenza Surveillance Network. The chosen strains are the H1N1, H3N2, and Type-B strains thought most likely to cause significant human suffering in the coming season (http://en.wikipedia.org/wiki/Influenza_vaccine#cite_note-102#cite_note-102).  

…[A]ntibodies made in response to vaccination with one strain of influenza viruses can provide protection against different, but related strains. A less than ideal match may result in reduced vaccine effectiveness against the variant viruses, but it still can provide enough protection to prevent or lessen illness severity and prevent flu-related complications. In addition, it’s important to remember that the influenza vaccine contains three virus strains so the vaccine can also protect against the other two viruses. For these reasons, even during seasons when there is a less than ideal match, CDC continues to recommend influenza vaccination. This is particularly important for people at high risk for serious flu complications and their close contacts.  http://www.cdc.gov/flu/about/qa/season.htm)

The composition of virus vaccines for use in the 2008-2009 Northern and Southern Hemispheres influenza season recommended by the World Health Organization on February 14, 2008 (http://www.who.int/csr/disease/influenza/vaccine_north2008_9/en/index1.html) was: 

• an A/Brisbane/59/2007 (H1N1)-like virus;
• an A/Brisbane/10/2007 (H3N2)-like virus (A/Brisbane/10/2007 was used at the time);
• a B/Florida/4/2006-like virus (B/Florida/4/2006 and B/Brisbane/3/2007 (a B/Florida/4/2006-like virus) were used at the time).  (http://www.who.int/csr/disease/influenza/recommendations2008_9north/en/index.html) and http://www.who.int/csr/disease/influenza/recommended_compositionFeb08FullReport.pdf)

 

The composition of virus vaccines for use in the 2009-2010 Northern Hemisphere influenza season recommended by the World Health Organization on February 12, 2009 http://www.who.int/csr/disease/influenza/vaccine_north2009_10/en/index1.html)  was:

an A/Brisbane/59/2007 (H1N1)-like virus;

• an A/Brisbane/10/2007 (H3N2)-like virus;
• a B/Brisbane/60/2008-like virus.  http://en.wikipedia.org/wiki/Influenza_vaccine#cite_note-101#cite_note-101 and (http://en.wikipedia.org/wiki/Influenza_vaccine#cite_note-102#cite_n)

H1N1 influenza-A is actually a hybrid or re-assortment of human, H5N1 avian virus and swine flu strains.