On December 17th, the Food and Drug Administration (FDA) approved a new 4-strain influenza vaccine (flu shot) for adults and children > 3 years old. Fluarix Quadrivalent (GlaxoSmithKline, GSK) is the first intramuscular vaccine to offer protection against 4 influenza strains.
Previously, I have written about what the influenza vaccine is and why it is so important to get immunized. The current available seasonal flu vaccine protects against the 3 influenza viruses (trivalent influenza vaccine) that research indicates will be most common during the upcoming season. The viruses in the vaccine can change each year based on international surveillance and scientists’ estimations about which types and strains of viruses will circulate in a given year. The current vaccine protects against 2 strains of influenza A virus and 1 strain of the influenza B virus. In 18 of the last 22 U.S. influenza seasons the viruses in the influenza vaccine have been well matched to the predominant circulating viruses. Preliminary data for the 2010-2011 influenza season indicate that influenza vaccine effectiveness was about 60% for all age groups combined (Unpublished CDC data).
However, over the past decade, there have been 2 circulating types of the influenza B virus in each influenza season. Since the current vaccine contains only 1 strain of the influenza B virus, this has led to an increased risk for influenza-related morbidity across all age groups. The new 4-strain vaccine continues to help protect against the 2 A strains, but now adds coverage against a second B strain. Dr. Leonard Friedland, V.P. and Head of GSK North America Vaccines Clinical Development and Medical Affairs said in a statement “[t]rivalent influenza vaccines have helped protect millions of people against flu, but in six of the last 11 flu seasons, the predominant circulating influenza B strain was not the strain that public health authorities selected”.
Experts now have a better chance of choosing the most prevalent strains of the virus for each flu season since they can now choose 4 strains instead of 3. This, in turn, will hopefully lead to increased protection from the flu for those of us who get vaccinated. The vaccine should be ready for the 2013-4 season flu season. There is another 4-strain influenza vaccine being developed Sanofi Pasteur but has not yet been approved by the FDA.
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Dr. Ananth Thyagarajan (Dr. T.)