Published Online: April, 2014
The Centers for Disease Control and Prevention (CDC) recommend receiving an annual seasonal influenza vaccine for all persons aged 6 months and older. In particular, the CDC recommends that individuals with chronic pulmonary disease, including asthma, receive this vaccine to limit influenza-related mortality and decrease transmission of the virus. Compliance rates with annual influenza vaccination have been low, historically, and have fallen well short of the goals targeted by the CDC through the Healthy People 2010 and 2020 initiatives.
Influenza and other respiratory viruses are risk factors for more severe and more frequent lower respiratory tract infections, as well as complications such as bronchiolitis, sepsis, and secondary bacterial infection. This month’s Journal of Allergy and Clinical Immunology (JACI) features a CME-series review by Dr. Matthew Greenhawt, MD, MBA, MSc, of the University of Michigan, exploring the evidence supporting vaccination as protection against influenza-related asthma exacerbations.
This review notes that only limited randomized, controlled evidence supports vaccination in preventing influenza-related asthma complications. A recent Cochrane Review noted that among 26 potential studies identified, only one included a randomized, controlled trial, which did not show benefit from vaccination apart from improvement in asthma-related quality of life, and no studies investigated preventing influenza-related asthma hospitalization. Apart from the Cochrane Review, other studies reviewed found vaccination was associated with reduced oral steroid use in asthma exacerbations and reduced severity-adjusted asthma exacerbations. One study noted vaccination was associated with increased odds of influenza-related hospitalization in asthmatic patients, and another that vaccination was associated with a higher rate of asthma- and pneumonia-related clinic visits.
Despite limited high-quality evidence (i.e. randomized, controlled trials), and some discrepancy as to the vaccine’s efficacy, this Journal article concludes that vaccination remains beneficial when weighing the benefits against the risks. There are clear data showing that persons with asthma are at higher risk for complications if they contract influenza, and the spread of influenza is best prevented by vaccination.
Annual vaccination is cost-effective for healthy adults aged 18-64 years. Therefore, until better means of preventing the virus are developed, children and adults with asthma should still receive annual vaccination, despite mixed evidence that it prevents influenza-related asthma exacerbation. Expert opinion on the matter has not waivered—if one prevents contraction of influenza, it reduces the likelihood of experiencing influenza-related asthma complications. The mixed evidence of large reviews on the subject may result from poor study design, cost limitations resulting in underpowered studies, or too short of an evaluation period for the effects of vaccination. Furthermore, these studies have not included data from the 2009 H1N1 pandemic, or take into account the introduction of quadravalent vaccines that cover both strains of Influenza B. Both of these factors need to be incorporated into future study of this issue, and may likely influence the efficacy of vaccination.
In conclusion, annual influenza vaccination remains the most effective way to prevent contracting influenza. Despite mixed evidence of whether or not vaccination prevents influenza-related asthma exacerbations in asthmatics, there are no better present options to prevent influenza. If one does not contract influenza, one cannot develop influenza-related asthma exacerbations, and therefore vaccination is still strongly favored by expert opinion.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.