Fever Incidence: Influvac Tetra vs TCV Vaccine
Influvac Tetra (inactivated influenza vaccine) has a higher incidence of causing fever compared to TCV (Typhoid Conjugate Vaccine), particularly in young children.
Fever Rates with Influvac Tetra
The inactivated influenza vaccine demonstrates variable fever rates depending on age and concurrent vaccination:
Young children (1-5 years): Postvaccination fever occurs in approximately 11.5-12% of children aged 1-5 years receiving inactivated influenza vaccine 1.
Older children: Fever rates decrease with age, affecting 4.6-5% of children aged 6-10 years and 5.1-5% of those aged 11-15 years 1.
Adults and elderly: Recent placebo-controlled trials show that split-virus influenza vaccines like Influvac Tetra are not associated with higher rates of systemic symptoms including fever compared to placebo in healthy young adults and older persons 1.
Concurrent vaccination significantly increases risk: When trivalent inactivated influenza vaccine (TIV) is administered simultaneously with PCV13 in children 6-23 months old, fever rates (≥38°C) reach 37.6% on days 0-1, compared to only 7.5% with TIV alone 2.
Influvac Tetra specifically: Clinical trials of Influvac Tetra showed overall adverse events were <1% and comparable to reference vaccines, with local and systemic reactions being minimal 3, 4.
Fever Rates with TCV (Typhoid Conjugate Vaccine)
The typhoid conjugate vaccine demonstrates an excellent safety profile with minimal fever risk:
Adverse event rates comparable to placebo: The oral Ty21a typhoid vaccine has adverse event rates of <1/100,000 doses, essentially comparable to placebo 5.
Excellent safety profile: The World Health Organization states that all typhoid vaccines, including TCV, demonstrate excellent safety profiles with mild, self-limited adverse events 5.
Vi polysaccharide vaccine: This parenteral typhoid vaccine causes injection site reactions but rarely systemic effects including fever 5.
No specific fever data: While the evidence confirms TCVs have minimal adverse events, specific fever incidence rates are not prominently reported, suggesting fever is not a common concern with these vaccines 5, 6.
Direct Comparison and Clinical Context
The key distinction is age-dependent:
In young children (6 months to 5 years), Influvac Tetra carries a substantially higher fever risk (11.5-37.6% depending on concurrent vaccines) compared to TCV's minimal fever profile 1, 5, 2.
In adults and older children, Influvac Tetra's fever risk approaches that of placebo, making the difference less clinically significant 1.
Fever with influenza vaccine is transient: When it occurs, fever begins 6-12 hours after vaccination and persists for only 1-2 days, most commonly affecting those with no prior exposure to influenza antigens 1.
Important Clinical Considerations
Simultaneous vaccination matters: The fever risk with influenza vaccines increases dramatically when given with other vaccines like PCV13, with an excess risk of 20-23 per 100 vaccinations 2.
Age is the critical factor: Young children receiving their first influenza vaccination have the highest fever risk, while previously vaccinated individuals and adults have minimal risk 1, 7.
TCV's safety advantage: The consistently low adverse event profile of TCV across all age groups makes it one of the better-tolerated vaccines available 5, 6.