Seasonal Influenza: Prevention with Vaccines
Seasonal Influenza: Prevention with Vaccines
Abstract & Commentary
By René J. Beckham, MD, Internal Medicine Consultant, National Imaging Associates, Phoenix, AZ, is Associate Editor for Urgent Care Alert.
Dr. Beckham reports no financial relationships relevant to this field of study.
Synopsis: Overview of prevention and treatment for influenza type A and B with inactive and live vaccines and antiviral medications.
Source: Targonski P, et al. Seasonal influenza: Prevention with influenza vaccines. Medscape 2006 Available at: www.medscape.com/viewprogram/6047.
Each year there are 20,000 to 40,000 deaths and up to 300,000 hospitalizations secondary to acute respiratory tract infections associated with influenza.1 Those at the highest risk for morbidity and mortality are elderly (65 years and older) adults, adults, and children with chronic health problems, and children age 6 months to 59 months.2 The usual months of influenza outbreak are October through May.
The recommendations regarding which strains of influenza A and B should be targeted in the upcoming year's vaccines are made the preceding February by the US Food and Drug Administration. These decisions are based on the new strains of viruses that may occur secondary to antigenic changes. The Centers for Disease Control and Prevention (CDC) then makes recommendations annually for prevention and treatment of the influenza outbreak.
There are 2 types of vaccines available to prevent influenza A and B. The first is the trivalent inactivated vaccine, or the flu shot, which has been recommended since 1963. Because it contains only inactivated and purified virus, it does not cause any influenza symptoms in patients who receive it. The CDC recommends giving the vaccine in the months of October and November; however, it can be given at any time throughout the influenza season. This vaccine does not prevent all patients from developing symptoms, but it can prevent hospitalizations and death in 70%-90% of healthy adults3 and 60%-80% in elderly debilitated patients.1 This lower effectiveness is presumed secondary to the blunted immune response to the vaccination in this population.
The less commonly utilized vaccine is the cold-adapted live attenuated intranasal vaccine. Although in the right population this form of vaccine is quite effective, its exact mechanism of protection is not clearly understood. Because it is a live virus, there is a chance of developing mild influenza symptoms after vaccination. Unlike the inactivated injected vaccine, this live vaccine is not recommended for those patients who may be immunocompromised, pregnant, or who have chronic pulmonary or cardiovascular conditions.
The second line of prevention and treatment of viral influenza are the antiviral agents. One class, the adamantanes, is not currently recommended as treatment for 2 reasons: influenza virus has developed a resistance to it over the past 3 years and it is only active against influenza A. The N-inhibitors include the medications oseltamivir and zanamivir, which are active against influenza A and B. These medications will decrease the duration of symptoms by 1-2 days in uncomplicated patients if they are started within 2 days of the onset of symptoms, and they may decrease the morbidity and mortality in high-risk patients. Both medications should be continued for 5 days when they are given for treatment; however, oseltamivir is approved for anyone older than 1 year, and zanamivir is only approved for patients older than 7 years.
The role of antiviral medications in prevention is secondary to vaccines; however, they can be given prophylactically in certain settings. During influenza outbreaks, they can be given to patients who have already been vaccinated or to those who are vaccinated at the time of the outbreak. For this purpose, they should be continued for a 2-week course at a dose of one time per day instead of 2 times per day, as in the treatment dosing.4
Commentary
Despite the continued effort to educate patients and health care workers regarding the importance of influenza vaccine and treatment, our vaccination rates remain low.5 Surprisingly, one of the groups with the lowest vaccination rates is health care workers.6 Increasing the vaccination rate throughout the population will significantly affect the morbidity and mortality in the elderly population and will positively affect the healthy population by decreasing days missed from work and school by illness.2 The medical community needs to improve its process of implementing influenza vaccination protocols to capture more patients, and it should improve utilization of antiviral medications when a patient presents with possible influenza symptoms.
References
- Smith NM, et al Prevention and control of influenza: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Tecomm Rep. 2006;55:1-42.
- Nichol KL. Improving influenza vaccination rates among adults. Cleve Clin J Med. 2006;73:1009-1015.
- Couch RB. Summary of medical literature. Review of effectiveness of inactivated influenza virus vaccine. In: Office of Technology Assessment, eds. Cost-Effectiveness of Influenza Vaccination. Washington, DC: Office of Technology Assessment; 1981:43-45.
- Mossad SB. Which agents should we use to treat and prevent influenza in 2006-2007? Cleve Clin J Med. 2006;73:1016-1018.
- van Essen GA, et al. Why do healthy elderly people fail to comply with influenza vaccination? Age Ageing. 1997;26:275-279.
- National Foundation for Infectious Diseases. Influenza immunization among health care workers. Call to action. Improving dismal influenza vaccination rates among health care workers requires comprehensive approach, institutional commitment. 2004;1.
Subscribe Now for Access
You have reached your article limit for the month. We hope you found our articles both enjoyable and insightful. For information on new subscriptions, product trials, alternative billing arrangements or group and site discounts please call 800-688-2421. We look forward to having you as a long-term member of the Relias Media community.