BETHESDA, Md. -- The National Foundation for Infectious Diseases (NFID) is issuing the following statement in light of two recent studies which have created some confusion about the importance of influenza immunization among the elderly (65+).
The first study, conducted by the National Institute of Allergy and Infectious Diseases (NIAID) [Archives of Internal Medicine, February 14, 2005], looked at overall influenza immunization rates and mortality rates in the 65+ population and concluded that despite increases in influenza immunization among this population, there was little change in mortality rates. This ecological study only looked at overall trends and did not look at whether the individuals who died were vaccinated or whether they had underlying conditions. Current Centers for Disease Control and Prevention (CDC) recommendations are based on observational studies, which compare vaccinated people with those who choose not to be vaccinated, and are considered by many experts, including the CDC, to be more appropriate than ecological studies for evaluating vaccine effectiveness.
To date, observational studies on influenza immunization have found the following:
The second study [American Journal of Epidemiology, February 14, 2005] notes that while influenza vaccination of the elderly has been shown to have a moderate, but important effect on mortality in that age group, as a nation, we have largely ignored one of the key vectors of influenza -- schoolchildren. The article proposes that future influenza prevention strategies add schoolchildren as a key target, which will reduce the spread of influenza to those at high risk for complications of the disease. The article concludes that the best strategy for minimizing the number of influenza-related deaths and morbidity for interpandemic influenza is to concentrate vaccine in both high-risk and high-transmitting population groups (schoolchildren) simultaneously. This approach will also support pandemic planning.
It is important to note that authors of both studies maintain that immunization of high-risk populations, including the elderly, remains an important public health strategy. They note that many previously published observational studies suggest a higher level of influenza vaccine effectiveness against death in the elderly than indicated in the NIAID paper.
The NFID wants to reinforce the importance of influenza immunization among persons age 65 and older, who are at high risk for complications, hospitalizations and death from influenza.
The overall body of scientific evidence about the vaccine efficacy and the public health impact of the disease supports current CDC recommendations, said William Schaffner, MD, NFID board member and professor and chairman, department of preventive medicine, Vanderbilt University School of Medicine. In addition, we hope that in the coming months, the immunization community engages in vigorous discussion about how to implement immunization of schoolchildren, based on sufficient availability of vaccine."
Source: The National Foundation for Infectious Diseases