What are the details and usage guidelines for Influvac Tetra (quadrivalent influenza vaccine) in various patient populations, including those with chronic medical conditions and the elderly?

Influvac Tetra: Quadrivalent Influenza Vaccine Overview

Influvac Tetra is a quadrivalent inactivated subunit influenza vaccine approved for use in individuals ≥6 months of age, demonstrating robust immunogenicity with seroprotection rates >90% for influenza A strains and 43-60% for B strains, alongside an excellent safety profile with adverse events <1%. 1, 2

Vaccine Composition and Technology

• Influvac Tetra is an egg-based, inactivated subunit vaccine containing four influenza strains (two type A and two type B) representing viruses likely to circulate in the upcoming season 1, 3
• The vaccine contains highly purified, inactivated surface antigens (hemagglutinin and neuraminidase) without whole virus particles 4, 3
• Manufacturing involves growth in embryonated hens' eggs, resulting in small amounts of residual egg protein; package inserts should be consulted for specific manufacturing details including preservatives and antibiotics used 4

Approved Patient Populations

Children (≥6 months)

• Approved for all children ≥6 months of age 1, 5
• Children <9 years who are previously unvaccinated require two doses administered at least 1 month apart for adequate immune response 4, 5
• Previously vaccinated children require only a single annual dose 4

Adults (18-60 years)

• Single dose provides adequate protection in healthy adults 2
• Vaccine effectiveness in this age group ranges from 70-90% when vaccine strains match circulating viruses 4

Elderly (>60 years)

• Single dose recommended annually 2
• While elderly patients develop lower postvaccination antibody titers than younger adults, the vaccine remains highly effective at preventing severe outcomes 4

Efficacy Data by Population

Healthy Adults and Children

• When vaccine and circulating strains are well-matched, efficacy is 70-90% in preventing laboratory-confirmed influenza illness 4, 5
• Reduces work absenteeism and healthcare resource utilization 4, 6
• Decreases influenza-associated otitis media in young children by approximately 30% 4, 6

Elderly and High-Risk Populations

• Most critically, the vaccine reduces mortality by 68-80% in elderly persons, even when efficacy against influenza illness itself is only 30-40% 4
• Prevents hospitalization for pneumonia and influenza by 30-70% in community-dwelling elderly 4
• Among nursing home residents, reduces hospitalization/pneumonia by 50-60% and death by 80% 4
• In children, vaccine effectiveness against influenza-associated death is 65% overall and 51% in those with underlying conditions 6

Immunogenicity Profile (Influvac Tetra Specific)

• Seroprotection rates >90% for influenza A strains (H1N1 and H3N2) 2
• Seroprotection rates 43-60% for influenza B strains 2
• Geometric mean fold increase ranges from 4.3-22.7 across all four strains 2
• Comparable immunogenicity in both adult (18-60 years) and elderly (>61 years) age groups 2

Chronic Medical Conditions

Priority Groups Requiring Annual Vaccination

• Chronic pulmonary disease (including asthma) 4, 6
• Chronic cardiovascular disease 4, 6
• Diabetes mellitus and other chronic metabolic diseases 4
• Renal dysfunction 4
• Hemoglobinopathies 4
• Immunosuppression (medication-induced, HIV, or transplant recipients) 4, 6
• Children/teenagers on long-term aspirin therapy (risk of Reye syndrome) 4

Special Considerations

• Patients with chronic conditions may develop lower antibody titers but still receive substantial protection against severe complications, hospitalization, and death 4
• Only inactivated vaccines (like Influvac Tetra) should be used in patients with chronic pulmonary conditions—never live attenuated nasal spray vaccines 6

Safety Profile

Common Adverse Events

• Local soreness at injection site (most frequent), typically lasting up to 2 days, mild and non-disabling 4, 7
• Systemic symptoms (fever, malaise, myalgias) beginning 6-12 hours post-vaccination, lasting 1-2 days, occurring no more frequently than placebo 4, 7
• Overall adverse events <1% in clinical trials of Influvac Tetra 2

Rare Adverse Events

• Immediate allergic reactions in patients with egg hypersensitivity (rare) 4, 7
• Guillain-Barré syndrome was associated only with the 1976 swine influenza vaccine and has NOT been associated with influenza vaccines since then 4, 7

Critical Safety Context

• The vaccine does not contain live virus and cannot cause influenza infection 4, 7
• The favorable safety profile far outweighs risks, especially given the 45-68% mortality reduction in elderly adults 7

Administration Guidelines

Dosing Schedule

• Annual vaccination required due to antigenic drift and waning immunity 4, 6
• Optimal timing: September through mid-November before influenza season 4
• Do not delay vaccination waiting for "optimal timing"—the risk of missing vaccination entirely outweighs timing concerns 6

Route and Site

• Intramuscular injection is the recommended route 4
• Adults and older children: deltoid muscle 4
• Infants and young children: anterolateral aspect of thigh 4

Healthcare Worker and Household Contact Vaccination

• Vaccination of healthcare workers is associated with decreased deaths among nursing home patients 4
• All physicians, nurses, hospital personnel, nursing home employees, and household members of high-risk patients should be vaccinated 4

Common Pitfalls to Avoid

• Do not assume prior vaccination provides multi-year protection—annual vaccination is mandatory 6
• Do not delay vaccination in high-risk patients for any reason—when multiple appropriate products exist, any licensed vaccine is acceptable 6
• Do not use expired vaccine from previous seasons—vaccine composition changes annually to match circulating strains 4
• Do not overlook racial and ethnic disparities—Black, Hispanic, and American Indian/Alaska Native children have 3-4 fold higher influenza-associated in-hospital deaths 6
• Do not withhold vaccination due to fear of side effects—the vaccine cannot cause influenza and serious adverse events are exceedingly rare 4, 7

Target Coverage Goals

• European Centre for Disease Prevention and Control recommends 75% vaccination coverage in at-risk groups and healthcare workers 1
• Current coverage remains far below recommended levels despite proven mortality and morbidity benefits 1