What are the recommendations for using Influvac Tetra (influenza vaccine) or Fluarix Tetra (influenza vaccine) in Singapore, specifically for high-risk groups?

Influenza Vaccination Recommendations for High-Risk Groups in Singapore: Influvac Tetra and Fluarix Tetra

Both Influvac Tetra and Fluarix Tetra are recommended for high-risk individuals in Singapore to reduce morbidity, mortality, and improve quality of life by preventing influenza and its complications. 1

Target Groups for Vaccination in Singapore

High-Priority Groups

• Persons aged ≥65 years 2
• Residents of nursing homes and chronic-care facilities 2
• Adults and children with chronic disorders of pulmonary or cardiovascular systems, including asthma 2
• Persons with chronic metabolic diseases (including diabetes mellitus), renal dysfunction, hemoglobinopathies, or immunosuppression 2
• Children and teenagers (6 months-18 years) receiving long-term aspirin therapy 2
• Pregnant women in the second or third trimester during influenza season 2

Transmission Prevention Groups

• Healthcare workers in hospital and outpatient settings 2
• Employees of nursing homes and chronic-care facilities 2
• Home care providers to high-risk persons 2
• Household members of high-risk persons 2

Vaccine Characteristics

Influvac Tetra

• Quadrivalent inactivated influenza vaccine 3
• Suitable for individuals from 6 months of age 3
• Demonstrated safety and immunogenicity across different age groups in studies including Asian populations 3

Fluarix Tetra

• Quadrivalent inactivated influenza vaccine 4
• Administered via intramuscular injection 4
• Can be given to anyone six months of age or older 4

Effectiveness and Benefits

• Vaccination can prevent illness in 70-90% of healthy persons when the vaccine strain matches the circulating strain 2
• For elderly persons with chronic illnesses, efficacy is lower but still attenuates infection severity 2
• Reduces pneumonia occurrence by 53%, hospitalization by 50%, and mortality by 68% 2
• In Singapore, influenza causes approximately 630,000 cases annually, resulting in 520,000 sick visits and 315,000 days of work absence 5
• Vaccination could potentially prevent 315,000 cases of influenza, 258,000 sick visits, 157,000 lost workdays, 2,100 hospitalizations, and 600 deaths annually in Singapore 5

Timing of Vaccination

• Annual vaccination is recommended as the viral strain changes yearly 2
• Optimal timing is before the influenza season begins 2
• In Singapore, influenza circulates year-round with less distinct seasonality than temperate regions 5, 6

Safety Considerations

Common Side Effects

• Local soreness at injection site (lasting up to 2 days) 2
• Systemic symptoms like fever, malaise, and myalgias (lasting 1-2 days) 2

Contraindications

• History of severe allergic reaction to previous influenza vaccination 2
• Severe egg allergy (though most egg-allergic individuals can receive influenza vaccines) 2

Special Considerations for Singapore

• Singapore's tropical climate means influenza can occur throughout the year, making timing of vaccination less seasonally dependent than in temperate regions 5
• A study in Singapore's long-term care facilities showed vaccine effectiveness of 40.5% overall, with higher effectiveness (59.3%) within 15-180 days post-vaccination 6
• The effectiveness was particularly good against influenza A(H3N2) at 67.9% within 15-180 days post-vaccination 6

Implementation Strategies

• Develop vaccination programs in outpatient clinics, emergency rooms, and walk-in clinics 2
• Implement vaccination programs in nursing homes, dialysis centers, and home care programs 2
• Use reminder systems and standing orders to improve vaccination coverage 2

Pitfalls and Caveats

• Vaccine effectiveness decreases with time since vaccination, with significantly lower protection after 180 days 6
• Effectiveness varies by influenza subtype and match between vaccine and circulating strains 4, 6
• Despite Singapore's significant disease burden from influenza, vaccination coverage remains below recommended levels 5, 3
• Vaccine efficacy is lower in elderly and immunocompromised persons compared to young healthy adults 4

Both Influvac Tetra and Fluarix Tetra are appropriate choices for high-risk individuals in Singapore, with selection based on availability, age of the recipient, and individual factors. Annual vaccination is crucial due to changing viral strains and waning immunity over time.