Flu vaccine shows lower efficacy than thought

According to a meta-analysis conducted by researchers at the University of Minnesota, the trivalent inactivated influenza vaccine had a pooled efficacy of 59 percent in people 18 through 64.
Michael Osterholm and his colleagues determined that there was no usable data on TIV efficacy in children ages two through 17 or adults 65 and older. The live attenuated vaccine was highly effective in children ages six months to seven years with a pooled efficacy of 83 percent, but there were no good data for older children or adults, MedPage Today reports.
"While the vaccine does work - and we still recommend that it be used - it does not deliver the levels of efficacy that have often been reported," Osterholm said in a podcast interview, according to MedPage Today.
William Schaffner of Vanderbilt University said that the results of the study will come as no surprise to "everyone who has been a scholar of influenza and influenza vaccines," according to MedPage Today.
"(The annual flu vaccine is) a pretty good vaccine, but not a great one," Schaffner said, MedPage Today reports. "Most years, it will prevent illness, it will prevent hospitalizations, and it will prevent deaths. It won't prevent them all and it cannot eradicate influenza."
Schaffner said that he hopes the study will spur the pharmaceutical industry and governments to put more resources towards improving the product. Until better vaccines are available, Schaffner said that the public should continue to get flu shots for the protection they do offer.
Osterholm and his colleagues read through 5,707 articles to come up with 31 studies that met strict criteria for inclusion and used the trials to generate estimates of efficacy, defined as relative reduction in influenza risk after vaccination. The authors said that the best results appear to come from LAIV in young children, but the Advisory Committee on Immunization Practices doesn't currently recommend it for them. They also noted that the pandemic vaccine effectiveness  is not adequate for a pandemic setting.
In an accompanying comment article, Health Kelly of the Victorian Infectious Disease Reference Laboratory in Melbourne, Australia, and Marta Valenciano of EpiConcept in Paris said that the new findings "understandably" have led Osterholm and colleagues to join in calls for better vaccines. In the meantime, they said that this new study should be used in public health policy.
"Now might also be an appropriate time to use revised estimates of the most probable effectiveness of influenza vaccines to re-examine the effectiveness and cost-effectiveness of some policy options," Kelly and Valenciano said, according to MedPage Today.