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It's unknown whether influenza vaccine helps the elderly

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By David Liu, PHD

Monday Aug 13, 2012 (foodconsumer.org) -- The majority of consumers for influenza vaccine are children and people aged 65 or older.   But a review study in Lancet Infectious Diseases found that no solid trials provide evidence to suggest that influenza vaccine protects the elderly.

The finding came after M.T. Osterholm of University of Minnesota and colleagues analysed 31 studies out of more than 5,000 studies/trials of influenza vaccines recorded in medical databases.

For the study, the researchers considered the 31 studies including 17 randomised controlled trials and 14 observational studies because they were published between Jan 1, 1967 and Feb 15, 2011 and used RT-PCR or culture to confirm influenza.

(Editor's note:  In most of cases as can be seen in this report, trials are conducted to see how an influenza vaccine triggers an immune response and they did not compare the incidence rate of influenza in the intervention arm with that in the control arm. This practice has drawn criticism because no data from such trials really directly indicate whether or not an influenza vaccine helps prevent influenza.)

Two types of influenza vaccines, trivalent inactivated vaccine (TIV) and live attenuated influenza vaccine (LAIV) were tested in the 31 trials.

The efficacy of the trivalent inactivated vaccine was found in 67 percent of the seasons analysed in ten randomized controlled trials, compared to 59 percent as pooled efficacy, in adults aged 18 to 65 years.  This type of vaccine was not tested for children aged 2 to 17 years and adults aged 65 years or older in trials that met the study inclusion criteria. That is, the efficacy of this type of vaccine remained unknown for these two age groups of people.

The efficacy of live attenuated influenza vaccine was shown in 75% of the seasons analysed in ten randomised controlled trials, compared to 83% as pooled efficacy, in children aged 6 months to 7 years. But no such trials for children aged 8-17 years met inclusion criteria.

Six (35%) of 17 analyses in nine trials showed significant protection against confirmed influenza in the outpatient or inpatient setting.  The median monovalent pandemic H1N1 vaccine effectiveness in five observational studies was on average 69%, meaning that 69 percent of vaccine recipients benefited from the vaccination.

The researchers concluded "Influenza vaccines can provide moderate protection against virologically confirmed influenza, but such protection is greatly reduced or absent in some seasons. Evidence for protection in adults aged 65 years or older is lacking. LAIVs consistently show highest efficacy in young children (aged 6 months to 7 years). New vaccines with improved clinical efficacy and effectiveness are needed to further reduce influenza-related morbidity and mortality."

Elderly people are at higher risk for influenza and its complications such as more severe secondary infections like pneumonia.  But no quality trials were ever conducted to generate evidence to show that use of an influenza vaccine would reduce the risk for the elderly people to acquire influenza.

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