Tom Jefferson and colleagues at the Cochrane Vaccine Field in Italy identified and assessed 274 studies on influenza vaccines and analysed their methodological quality, prestige of the host journals (impact factor) and citation rates in the scientific literature.

They found no relationship between study quality, publication in prestige journals or their subsequent citation in other articles. They also found that influenza vaccine studies are of poor quality and those with conclusions in favour of the vaccines are of significantly lower methodological quality.

The single most important determinant of where the studies were published or how much they were cited was sponsorship. Those partially or wholly funded by industry had higher visibility.

The researchers also found no relationship between journal impact factor and the quality of the influenza vaccine studies it publishes, suggesting that the impact factor is not the robust quality indicator that publishers suggest and confirming some of the widely expressed doubts on its appropriateness as a means of rewarding researchers with promotions and funds.

Dr Jefferson concludes: "The study shows that one of the levers for accessing prestige journals is the financial size of your sponsor. Pharmaceutical sponsors order many reprints of studies supporting their products, often with in-house translations into many languages. They will also purchase publicity space on the journal. Many publishers openly advertise these services on their website. It is time journals made a full disclosure of their sources of funding."

Note: If no author is given, the source is cited instead.

• Vaccines
• Influenza

• Bird Flu Research
• Nature

• Funding Policy
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• Evidence-based medicine
• Vaccination
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