Please see the preliminary recommendations at the end of this article.

How Effective is the Seasonal Influenza Vaccine?
The effectiveness of the vaccine depends, in part, on the match between the viruses in the vaccine and influenza viruses that are circulating in the community. However, it’s important to remember that even when the viruses are not closely matched, the vaccine can still protect many people and prevent flu-related complications.

As of February 9, 2008, nearly all H1N1 viruses tested at CDC were well-matched to the H1N1 vaccine strain. However, most of the H3N2 and B virus strains were different from those contained in the vaccine. This suggests that protection against circulating H3N2 and B virus strains may not be optimal. As stated above, however, even when the viruses are not closely matched, the vaccine can protect many people and prevent flu-related complications. Therefore, the CDC continues to recommend influenza vaccination even during seasons when there is a less than ideal match. This is particularly important for people at high risk for serious flu complications and their close contacts.

The provisional recommendations for the prevention and control of influenzain the 2008 — 2009 flu season include the following:

• Annual vaccination of children aged 6 months — 59 months should continue.
• Annual vaccination for all children aged 6 months — 18 years.
• Annual vaccination for all children aged 6 months — 18 years should begin no later than during the 2009 - 2010 influenza season.
• If feasible, annual vaccination of all children aged 5 years — 18 years should begin in 2008 when the vaccine for the 2008 - 2009 influenza season becomes available.
• Persons at higher risk of influenza complications because of underlying medical conditions, children aged 6 months — 23 months, and persons aged >49 years should receive TIV. Either trivalent inactivated influenza vaccine (TIV) or live, attenuated influenza vaccine (LAIV) should be used when vaccinating persons aged 2 — 49 years who do not have medical conditions that put them at higher risk for influenza complications.
• Children aged 6 months — 8 years should receive 2 doses of influenza vaccine (doses separated by >4 weeks) if they have not been vaccinated
  previously at any time with at least one dose of either LAIV or TIV.
• Clinicians and immunization program staff should screen for possible reactive airways diseases when considering use of LAIV for children aged 2 — 4 years, and should avoid use of this vaccine in children with asthma or a recent wheezing episode. The ACIP has previously provided recommendations on screening for possible reactive airways diseases in children aged 2 — 4 years.
• Recommendations for annual vaccination of persons in other age or risk groups were not changed, and can be found in Prevention and Control of Influenza: Recommendations of the ACIP, 2007.
• The 2008 — 2009 trivalent vaccine virus strains are A/Brisbane/59/2007 (H1N1)-like, A/Brisbane/10/2007 (H3N2)-like, and B/Florida/4/2006-like antigens. All three strains are different from the 2007-2008 Northern Hemisphere influenza vaccine.
• The antiviral medications recommended for chemoprophylaxis or treatment of influenza (oseltamivir or zanamivir) have not changed for the 2008 - 2009 influenza season.