Jojy Cheriyan MD, MPH- Jan16, 2015

This year's flu vaccine is not working as expected, and the report issued yesterday by the Centers for Disease Control (CDC)  estimated that the effectiveness of this year's Flu Vaccine has been declined to just 23 %.  Last month the effectiveness was reported as 40 % . This is due to a mismatch with the predominant H3N2 virus strain.

This year, scientists noticed that influenza A (H3N2) — the dominant strain in circulation — began mutating almost immediately. This mutation in turn changes the virus, making the antibodies acquired through vaccination ineffective. About 68% of these viruses have now "drifted" to be genetically different from the flu viruses used in vaccines. Scientists use the previous year's viruses to prepare the vaccine for the next year.

The surveillance reports show that Influenza is spreading coast to coast and almost all States have reported marked rise in the incidence rates. The CDC still recommends that people get flu shots. Fewer than half of Americans have been vaccinated this year, slightly less than usual.

The Flu Vaccine we use currently can protect against three to four different strains of flu viruses. Therefore  it is always recommended to get vaccinated. Some strains show up late in the season and you may get protection if you are vaccinated.

The CDC is also urging patients and health care providers to make greater use of antiviral drugs, such as Tamiflu (Oseltamivir)  and Relenza (Zanamivir). If taken within the first 24 to 48 hours after symptoms appear, antivirals can reduce the length of time that people are sick by one or two days.

Antivirals also reduce the risk of serious complications and hospitalizations. After 48 hours, the effect of these antivirals also declines, but may benefit elderly people and people who have other medical conditions.