Which vaccine has a higher incidence rate of inducing fever in a 6-month-old baby, Influvac Terra (influenza vaccine) or TCV (tetanus, conjugate vaccine)?

Which Vaccine Has a Higher Fever Incidence in 6-Month-Old Infants?

Influvac (influenza vaccine) has a significantly higher incidence of fever compared to TCV (typhoid conjugate vaccine) in 6-month-old infants, with fever rates ranging from 11.5-37.6% depending on co-administration with other vaccines, while TCV data for this age group is limited as it is typically not administered at 6 months.

Fever Rates with Influenza Vaccines (Including Influvac)

Age-Specific Fever Incidence

• Infants aged 6-23 months experience fever in approximately 10-35% of cases within 24 hours after influenza vaccination, which is substantially higher than older children 1
• Among children aged 1-5 years, fever occurs in 11.5% after influenza vaccination 2
• High-risk infants aged 6 months to 4 years show even higher rates, with fever reported in up to 27% of cases 2

Influvac-Specific Data

• A comparative study in New Zealand found that Influvac had significantly higher fever rates than some other influenza vaccine brands, though lower than Fluvax 3
• Influvac recipients had an odds ratio of 0.54 (95% CI 0.36-0.81) for fever compared to baseline, indicating moderate reactogenicity 3
• The fever typically begins 6-12 hours post-vaccination and persists for 1-2 days 2, 4

Co-Administration Effects

• When influenza vaccine is given simultaneously with PCV13, fever rates increase dramatically to 37.6% in children aged 6-23 months 5
• This represents an excess risk of 20-23 additional fever cases per 100 vaccinations compared to either vaccine alone 5

TCV (Typhoid Conjugate Vaccine) Considerations

Critical Age Limitation

• TCV is typically not administered to 6-month-old infants as it is generally recommended for children ≥6 months in endemic areas, but more commonly started at 9-12 months or older
• No direct comparative data exists for TCV fever rates in 6-month-olds in the provided evidence

Clinical Context

• The question appears to compare vaccines that are not typically given at the same age, making direct comparison challenging
• If the question refers to a different vaccine abbreviation (such as a tetanus-containing vaccine), this would need clarification

Important Clinical Caveats

Fever Management

• Acetaminophen 10-15 mg/kg every 4-6 hours can be used for fever management, but routine prophylactic use is not recommended for healthy infants 4
• Prophylactic antipyretics are only recommended for infants with a history of seizures or family history of convulsions 4

Distinguishing Vaccine-Related Fever

• Fever ≥40.5°C (≥105°F) within 48 hours constitutes a severe reaction requiring VAERS reporting 4
• The influenza vaccine cannot cause actual influenza infection—it contains only inactivated viruses 1, 6
• Respiratory symptoms occurring after vaccination often represent coincidental illness unrelated to the vaccine 6

Ethnic and Individual Variations

• European ethnicity and second vaccine doses are associated with higher fever reporting after influenza vaccination 3
• Reactogenicity profiles vary between different influenza vaccine brands, necessitating consideration of specific product characteristics 3