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| |  Administration of Paracetamol to Children Receiving Vaccinations Can Reduce Vaccine Response NEW YORK -- October 15, 2009 -- Although prophylactic paracetamol reduces post-vaccination fever, it also reduces the child’s response to some of the vaccine antigens, according to a study published in this week’s edition of The Lancet. Thus use of prophylactic paracetamol can no longer be routinely recommended in this setting. Roman Prymula, MD, University of Defence, Hradec Kralove, Czech Republic, and colleagues conducted 2 randomised controlled trials -- 1 at the time of initial childhood vaccinations, and the other at the time of booster injections. The vaccinations were the routine vaccinations offered to children in developed nations, to offer protection against pneumococcal disease, Haemophilus influenzae type b, diphtheria, tetanus, whooping cough, hepatitis B, polio, and rotavirus. Infants from 10 centres in the Czech Republic were randomly assigned to receive 3 prophylactic paracetamol doses every 6 to 8 hours in the first 24 hours after vaccination (n = 226), or no paracetamol (n = 233). The primary aim of the study was the reduction in fever of 38oC or higher, while the secondary aim was to analyse immunogenicity of the administered vaccines. The researchers found that, after initial vaccinations, a lower proportion of infants in the paracetamol group had temperatures above 38oC compared to the control group (42 % vs 66%, respectively). Similar results were observed after booster vaccinations (36% in prophylactic paracetamol group vs 58% in control). Geometric mean concentrations (GMCs) were significantly lower in the paracetamol group than in the control group, for antibodies against the pneumococcal serotypes contained in the vaccine, Haemophilus influenzae type b, diphtheria and tetanus toxoids, and for one of the whooping cough antibodies. After booster vaccinations, lower antibody GMCs persisted in the paracetamol group for tetanus toxoid and most pneumococcal serotypes. “To our knowledge, such an effect of prophylactic paracetamol on postimmunisation immune responses has not been documented before... the interference of paracetamol on antibody responses could result from the prevention of inflammation,” the authors wrote. The authors postulate that prophylactic paracetamol could reduce immune responses because it interferes with the early phase of post-vaccination immune reactions that require interaction between different cells of the immune system. But for this hypothesis to be correct, paracetamol should interfere with responses only if administered at the time of or early after immunisation. Their analysis of the data confirmed this. They also analysed 10 previous studies, and their findings supported the hypothesis that paracetamol maximally interferes with vaccine responses if administered early, whereas if used therapeutically once fever and the corresponding inflammatory signals have already been established, its effect (if any) can be expected to be smaller. “The clinical relevance of these immunological findings is unknown and needs further assessment,” the authors concluded. “Prophylactic administration of antipyretic** drugs at the time of vaccination should nevertheless no longer be routinely recommended without careful weighing of the expected benefits and risks.” SOURCE: The Lancet
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