Pandemic (H1N1) 2009 flu vaccine
When the pandemic began in April 2009, at least 20 companies began working on a vaccine. Eventually, several different manufacturers developed monovalent vaccines for H1N1 2009. Monovalent means the vaccine contained just one virus - the one causing the pandemic. Ordinary seasonal flu vaccines are trivalent and contain three different viruses. These are selected on the experts' best guess as to what flu viruses will be most common in the upcoming flu season. The pandemic H1N1 virus was included as an ingredient in all seasonal 2010-2011 flu vaccines. A separate pandemic-only vaccine is no longer necessary.
In 2009, the pandemic-only monovalent vaccines were initially purchased by many governments. Supply was initially low, leaving health authorities within each country to decide who should receive the vaccine (ie. whether it should be restricted to certain priority groups.) Availability varied by country, and some could not afford the vaccines. Some underresourced nations relied on a WHO stockpile to provide some doses.
Pandemic vaccines later became available to private entities in some countries. Some nations ended up with a surplus of vaccine, as interest in vaccination was lower than expected and the products only required one dose. When initially ordering, many governments procured enough vaccine to give citizens two doses, since initial data indicated people might need a second dose for more complete protection.
Seasonal influenza vaccine
Seasonal flu vaccines are those offered to the public every year as flu season approaches. They are designed to help protect people from infection during the upcoming, seasonal waves of flu activity.
Generally, most people should get a flu shot every year as a good health practice. The seasonal flu vaccines currently available provide protection against the pandemic H1N1 flu virus.
As a general good health practice, people should ensure their routine vaccinations are up-to-date. This includes pneumocococcal vaccination for certain adults: those over 65, people with serious long term health conditions and people whose immune systems are compromised due to transplants, cancer treatments, HIV/AIDS, etc. See the CDC info sheet (http://www.cdc.gov/vaccines/Pubs/vis/downloads/vis-ppv.pdf) for more details.
For further details on pandemic-only vaccines see: