What is Influenza (Human influenza)?

From the Guidelines

Influenza prevention through annual vaccination is the most effective method to reduce morbidity, mortality, and improve quality of life, especially in high-risk populations such as children, older adults, and individuals with underlying medical conditions. The influenza virus can cause severe illness and complications, particularly in vulnerable populations, with rates of serious illness and death highest among children younger than 2 years, seniors 65 years and older, and people of any age with medical conditions that place them at increased risk of having complications from influenza 1. Some key points to consider include:

• Influenza is spread from person to person primarily by droplets of respiratory secretions expelled by coughing or sneezing, and can also be spread by direct contact with influenza virus-contaminated surfaces 1.
• Annual hospitalization rates for laboratory-confirmed influenza in children younger than 6 months can range from 240 to 720 per 100,000 healthy children, and 17 to 45 per 100,000 for children 2 to 5 years of age 1.
• The risk of complications is increased among pregnant women, individuals with underlying chronic cardiopulmonary conditions, individuals with certain neuromuscular conditions, and immunocompromised people 1.
• Vaccination is the best method of prevention, and antivirals can also be used as a primary or secondary means of preventing influenza transmission in certain settings 1.
• The Infectious Diseases Society of America (IDSA) provides recommendations on the use of trivalent inactivated and live attenuated vaccines, as well as diagnosis, treatment, and chemoprophylaxis with antivirals 1. In terms of treatment, oseltamivir (Tamiflu) and zanamivir (Relenza) are recommended as first-line antiviral therapy for influenza, with dosing regimens varying depending on age, weight, and renal function. For example, oseltamivir can be given at a dose of 75 mg twice daily for adults, or 3-5 mg/kg/dose twice daily for children, for 5 days 1. It's also important to note that influenza vaccination is recommended for all individuals 6 months of age and older, with certain exceptions, such as those with severe allergic reactions to previous influenza vaccinations. Overall, prevention and treatment of influenza require a comprehensive approach, including vaccination, antiviral therapy, and infection control measures, to reduce the risk of complications and improve outcomes.

From the FDA Drug Label

For subjects infected with type B virus, the median time to improvement of influenza symptoms was 75 hours in the XOFLUZA group (95% CI of 67,90) compared to 101 hours in the placebo group (95% CI of 83,116). The predominant influenza virus strain in this trial was the A/H3N2 subtype (67%), followed by A/H1N1 (20%) and type B (9%). In subjects that were 5 years of age and older, there was a statistically significant reduction in the proportion of household contacts (subjects) with laboratory-confirmed clinical influenza from 13% in the placebo group to 2% in the XOFLUZA group In the 108 pediatric subjects 5 to less than 12 years of age enrolled in Trial T0834, 57 subjects received XOFLUZA and 51 received placebo. In this age group, the proportion of subjects with laboratory-confirmed clinical influenza was 4% in the XOFLUZA group and 14% in the placebo group.

Efficacy of Baloxavir Against H. Influenza

• The median time to improvement of influenza symptoms was 75 hours in the XOFLUZA group compared to 101 hours in the placebo group for type B virus.
• Baloxavir reduced the proportion of household contacts with laboratory-confirmed clinical influenza from 13% in the placebo group to 2% in the XOFLUZA group.
• In pediatric subjects 5 to less than 12 years of age, the proportion of subjects with laboratory-confirmed clinical influenza was 4% in the XOFLUZA group and 14% in the placebo group 2.

From the Research

H. Influenza

• Influenza is a significant cause of morbidity and mortality, particularly in older adults and critically ill patients 3, 4.
• The most vulnerable population to the effects of influenza are older adults, who have age-related characteristics that make their response to both infection and therapeutics different than younger patients 3.
• Influenza vaccination and antiviral therapy are the foundational approaches to preventing and treating influenza in geriatric patients 3.
• There are five antivirals used in influenza, including oseltamivir, zanamivir, peramivir, laninamivir, and baloxavir marboxil 5, 6, 4.
• Oseltamivir has the most abundant evidence, including in the hospital and long-term care facilities, and the strongest evidence for reducing mortality and complications 3.
• Peramivir offers the shortest time for symptom alleviation, while baloxavir is best tolerated 3, 6.
• The appropriate use of antivirals requires further study, particularly in critically ill patients and hospitalized patients 6, 4.
• Neuraminidase inhibitors, such as oseltamivir, zanamivir, and peramivir, constitute the vast majority of antivirals currently prescribed for influenza, but data on their efficacy in critically ill patients is limited 4.
• Oseltamivir and zanamivir have been shown to be effective in preventing influenza in a range of population subgroups, including healthy adults, at-risk elderly subjects, and pediatric contacts 7.