Flu Vaccine for All: A Critical Look at the Evidence

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SOURCE:   Medscape
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Does the evidence support the call for universal influenza vaccination?

Response from Eric A. Biondi, MD, MS
Assistant Professor of Pediatrics, Pediatric Hospitalist, University of Rochester Medical Center, Rochester, New York
Response from C. Andrew Aligne, MD, MPH
Assistant Professor of Pediatrics, Director of The Hoekelman Center, University of Rochester School of Medicine & Dentistry, Rochester, New York

Influenza vaccination is a yearly ritual. The Advisory Committee on Immunization Practices (ACIP) and the American Academy of Pediatrics (AAP) recommend annual influenza vaccination for all healthy persons 6 months of age or older who are without contraindications.

In an interview published in The Atlantic, Tom Jefferson, head of the Vaccine Field Group at the Cochrane Database Collaboration (the world’s leading producer of evidence-based medical reviews), voiced serious reservations about the data supporting influenza vaccine recommendations, stating that “The vast majority of the studies [are] deeply flawed. Rubbish is not a scientific term, but I think it’s the term that applies.”

A critical look at the evidence raises further questions about the flu shot recommendations. A 2012 Cochrane review examining the efficacy of pediatric influenza vaccination noted that:

…industry-funded studies were published in more prestigious journals and cited more than other studies, independent of methodological quality and size. Studies funded from public sources were significantly less likely to report conclusions favorable to [influenza] vaccines… reliable evidence on influenza vaccines is thin but there is evidence of widespread manipulation of conclusions and spurious notoriety of the studies.

And a 2014 Cochrane review examining use of flu vaccine in healthy adults, including pregnant women, concluded that:

[Influenza] vaccination shows no appreciable effect on working days lost or hospitalization.

Read about the virology of influenza and it’s relationship with vitamin D.

Summing Up the Data

A 2012 systematic review and meta-analysis examined the efficacy and effectiveness of licensed influenza vaccines in patients with confirmed influenza illness. The authors confirmed that the original “recommendation to vaccinate the elderly was made without data for vaccine efficacy or effectiveness.” The main message was that we need a better vaccine and better studies to demonstrate its effectiveness.

Despite the lack of high-quality data supporting the value of the flu shot, widespread vaccination policy might still be reasonable if observational studies consistently showed a benefit. However, the observational studies cited by flu shot proponents are frequently flawed. In many studies, relevant clinical outcomes are ignored in favor of immunogenicity (ie, the ability to elicit an antibody response). “Influenza-like illness” (ie, cold symptoms) is frequently measured instead of serious outcomes, such as pneumonia or death. When these more serious outcomes are examined, there is often a failure to control for healthy user bias—the propensity for healthier people to do such things as receive annual check-ups, eat healthier foods, and get the flu shot. So, although it’s true that people who get flu shots live longer, it may have nothing to do with actually getting the flu shot.

A 2005 study of a 33-season, national data set attempted to reconcile the reduced all-cause morbidity and mortality found in some observational studies of influenza vaccination with the fact that “national influenza mortality rates among seniors increased in the 1980s and 1990s as the senior vaccination coverage quadrupled.” In this study, the authors conclude that:

“[Our] estimates, which provide the best available national estimates of the fraction of all winter deaths that are specifically attributable to influenza, show that the observational studies must overstate the mortality benefits of the vaccine…[even during two pandemic seasons] the estimated influenza-related mortality was probably very close to what would have occurred had no vaccine been available.”

The rationale for flu immunization as a national health priority is that influenza is a disease with serious complications, such as pneumonia, hospitalization, and death. If the reason for influenza vaccination is that flu is such a serious disease, then the relevant outcomes are whether vaccination improves morbidity and mortality from flu. However, after decades of vaccine use, it is hard to detect any public health impact. This is in stark contrast to other routine vaccinations, such as polio and Haemophilus influenzae type b, where introduction of the vaccine led to obvious decline of the disease.

We are pediatricians, and we believe in childhood immunizations. Many vaccines have provided immense public health value. We simply question whether the policy of routine influenza vaccination has outpaced the data supporting its use.

Influenza vaccination now supersedes many other priorities of public health (such as obesity, illiteracy, and high school dropout), and we question whether so much time, effort, and money should be dedicated to flu vaccination while these other national healthcare priorities remain on the back burner.

References are available in the original article on Medscape.

Read about the virology of influenza and it’s relationship with vitamin D.