Overall, 5% to 10% of the prophylaxis group had fever on Day 1 or 2 after vaccination, compared with 10% to 20% of the placebo group (no P value given). Antipyretic use produced lower antibody GMC responses for antipertussis and antitetanus vaccines at 5 months but not at 13 months. Patients achieved the prespecified effective antibody levels at both 5 and 13 months, regardless of intervention.
Antipyretics don’t affect immune response with inactivated flu vaccine
A 2017 RCT investigated the effect of either prophylactic acetaminophen (15 mg/kg every 4 to 6 hours for 24 hours) or ibuprofen (10 mg/kg every 4 to 6 hours for 24 hours) on immune response in children receiving inactivated influenza vaccine.3 Researchers randomized 142 children into 3 treatment groups (acetaminophen, 59 children; ibuprofen, 24 children; placebo, 59 children). They defined seroconversion as a hemagglutinin inhibition assay titer of 1:40 postvaccination (if baseline titer was less than 1:10) or a 4-fold rise (if the baseline titer was ≥ 1:10).
All interventions resulted in similar seroconversion rates for all A or B influenza strains investigated. Vaccine protection-level responses ranged from 9% for B/Phuket to 100% for A/Switzerland. The trial didn’t report febrile reactions or infection rates.
RECOMMENDATIONS
In 2017, the Advisory Committee on Immunization Practices (ACIP) issued guidelines generally discouraging the use of antipyretics at the time of vaccination, but allowing their use later for local discomfort or fever that might arise after vaccination. The guidelines also noted that antipyretics at the time of vaccination didn’t reduce the risk of febrile seizures.4
Editor’s takeaway
Although ACIP doesn’t encourage giving antipyretics with vaccines, moderate-quality evidence suggests that prophylactic acetaminophen reduces fever and pain after immunizations by a reasonable amount without an apparent clinical downside.