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European investigators assessed the effect of prophylactic acetaminophen on fever and immunogenicity in children receiving routine primary and booster immunizations. Two randomized, non-blinded, controlled, open-label trials were conducted in 10 centers in the Czech Republic between 2006 and 2007. Study participants, healthy infants 9 to 16 weeks of age at the start of the study, were immunized with 10-valent pneumococcal, non-typeable Haemophilus influenzae protein D-conjugate vaccine (PHiD-CV) and hexavalent diphtheria-tetanus-3-component acellular pertussis-hepatitis B-inactivated poliovirus types 1, 2, and 3-Haemophilus influenzae type b vaccine (DTPa-HBV-IPV/Hib). These vaccines were given at 3, 4, and 5 months of age while oral rotavirus vaccine was given at 3 and 4 months of age. Booster doses of PHiD-CV and DTPa-HBV-IPV/Hib were given at 12 and 15 months of age.
Participants were randomized to receive prophylactic acetaminophen (226) or no prophylaxis (233). Those in the acetaminophen group received three prophylactic doses every 6 to 8 hours in the first 24 hours after each vaccination with the first dose given immediately after vaccination. The dose of acetaminophen was 80 mg for infants weighing between 4.5 kg and 7 kg and 125 mg for those weighing more than 7 kg. Therapeutic use of antipyretics was allowed for both groups.
To evaluate immunogenicity, blood samples were collected before and one month after both primary and booster immunizations. Re-actogenicity data were collected on diary cards completed by parents or guardians on the day of vaccination and for three subsequent days after each vaccine dose.
Four hundred fifty-nine children received primary vaccines and 414 booster immunizations. Mean age at the onset of primary immunization was 12.3 weeks and 12.7 months at the time of boosting. High grade fever (>39.5°C) was uncommon in both groups after primary (<1%) and booster (<2%) immunizations. However, temperatures >38°C after at least one dose were more common in the control group after both primary (66% vs 42.5%) and booster (58% vs 36%) immunizations.
The vaccines were highly immunogenic in both groups. Antibody geometric mean concentrations were significantly lower in the acetaminophen group after primary vaccination for all 10 pneumococcal vaccine serotypes and for Haemophilus, pertussis, diphtheria, and tetanus vaccines.
Even after boosting, lower antibody geometric mean titers persisted in the children randomized to the acetaminophen group for tetanus, Haemophilus, and 9 of 10 pneumococcal serotypes. The authors conclude that acetaminophen use after immunization reduced the risk of febrile reactions, but reduced the immune response to vaccine components.
Some clinicians routinely advise antipyretic administration in infants and children receiving vaccines. The rationale is that the antipyretic will reduce painful and febrile reactions, although the evidence supporting such a recommendation is scant. In a twist, the authors of the current study report on the...
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