This vaccine is indicated for persons in high-risk groups similar to those for whom influenza vaccination has been recommended in recent years. Both forms of vaccine are produced from egg cultures and are formalin inactivated. Immunogenicity and side effects of split virus and whole virus vaccines are similar in adults when the vaccines are used according to the recommended dosage. Influenza generally appears in the United States in October. Although widespread trials are lacking, influenza vaccine is estimated to be 90 percent effective in preventing symptomatic disease in recipients who are young and healthy.
Vaccination also has substantial economic benefits for healthy working adults.
The vaccine is least effective in elderly or chronically ill patients, such as transplant recipients. However, a meta-analysis of 20 studies of influenza vaccinations in the elderly demonstrates a 56 percent efficacy in preventing respiratory illness and a 65 percent efficacy in preventing death. Unfortunately, fewer than 30 percent of patients who are at high risk receive the vaccine each year, even though the vaccine is cost-effective. People 65 years of age or older. Residents of nursing homes and other long-term care facilities housing patients of any age with chronic medical conditions.