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Flu vaccine ineffective for those over 65 reports CDC

Robin Wulffson MD's picture
flu, flu vaccine, ineffective, seniors, deaths, hospitalizations

This year’s particularly nasty flu season has hit two age groups to a greater degree and others: young children and seniors. Hospitalizations and deaths have been some of the highest ever recorded for the elderly. The Centers for Disease Control and Prevention (CDC) has an explanation. The agency found that only 9% of individuals age 65 and older have benefited from the flu vaccine this year. Despite that poor response rate, the CDC is still recommending that seniors receive the vaccine. The agency notes that the vaccine is effective in younger individuals—anyone over six months of age.

The statistics were presented in the CDC’s Weekly Morbidity and Mortality Report released on February 21. The finding that only 9% of seniors benefited from the vaccine represents a level too low to be statistically significant; however, the CDC notes that even a small amount of protection is better than none. In addition to the foregoing, the study found that the vaccine has reduced hospitalizations and deaths among seniors. However, because of the limited protection that the vaccine may offer, the agency recommends that seniors who have been vaccinated and develop flu symptoms should seek prompt medical attention. For younger individuals, the vaccine has been found to reduce the need to see a physician for an infection by one-half to two-thirds. The latest CDC report was based on a survey of 2,697 children and adults by the U.S. Influenza Vaccine Effectiveness Network from December 3, 2012, through January 19, 2013.

This season’s flu hospitalization rate for seniors is the highest since CDC began its current surveillance system in 2007. In the last week of January, the rate of individuals aged 65 or older who were hospitalized with a laboratory-confirmed case of influenza was 116 per 100,000. Previously, the highest rate was 73.7 per 100,000. The CDC has no explanation for the ineffectiveness of the vaccine for seniors; however, one factor is that as people age, their immune system tends to become less effective in warding off infection.

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The CDC notes that its findings are similar to those conducted this flu season in Europe. The agency also cautioned that the findings were interim and only assessed individuals who saw a physician for flu symptoms. The CDC researcher plan to do further research to determine whether chronic medical conditions and other problems associated with aging might have affected the outcome.

For this entire flu season, the CDC has noted that the vaccine is far from 100% effective for any age group. The present study has found that the vaccine’s overall effectiveness for individuals over six months of age is just 56%; this figure is lower than the 62% rate that had been estimated earlier in the season. This season’s vaccine contains protection against three flu strains: H3N2, influenza B, and H1N1. The CDC has found that the vaccine was 67% effective against influenza B in adults over 65 but only 9% effective against H3N2, which is the most prevalent strain this season. The CDC notes that there were not enough H1N1 cases to determine its effectiveness. In view of the study’s findings, the members of the CDC’s advisory panel are of the impression that a new and improved vaccine needs to be developed.

The vaccine’s overall effectiveness against H3N2 flu by age group was found to be:

  • 6 months to 17 years: 58%.
  • 18 to 49 years: 46%.
  • 50 to 64 years: 50%.
  • 65 and older: 9%.

Reference: CDC