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Paracetamol may lower antibody response

The Lancet has published the results of a study indicating that antibody response to vaccination may be reduced by the concurrent administration of paracetamol. These results have been reported in the wider media (BBC).

The study was conducted in the Czech Republic and recruited 459 healthy infants. The study was open-label with participants being assigned to taken 3 doses of paracetamol at 6-8 hourly intervals after immunisation (n=226) or to give no prophylactic paracetamol (n=233). Participants were administered with a primary vaccination course at 3, 4 and 5 months of age and then a booster dose between 12 and 15 months of age. The vaccinations used differ from those recommended in the UK and included pneumococcal non-typeable Haemophilus influenzae protein D-conjugate vaccine (PHiD-CV), hexavalent diphtheria, tetanus, 3-component acellular pertussis, hepatitis B, inactivated poliovirus types 1 and 2, and 3-H influenzae type b vaccine (DTPa-HBV-IPV/Hib) and oral human rotavirus vaccine (HRV).

The primary objective of the study was to assess fever response in the total cohort with a secondary objective to assess immunogenicity of the vaccines. Incidence of fever (temperature of 38C or greater) was significantly lower in participants who received paracetamol in the primary (42% versus 66%) and booster studies (58% versus 36%). Fever greater than 39.5C was uncommon and occurred in 9 participants of the entire study. However, it was also noted that antibody response (measured by geometric mean concentration) was lower in the group who received paracetamol. Rates of seroconversion were still high in both groups, especially after administration of the booster dose.

The authors conclude that, "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".

Action: Clinicians should be aware of these findings and the wider media coverage. Parents should be advised to avoid administering paracetamol unless deemed clinically necessary and reassured that seroconversion rates were still high after completion of the vaccination schedule.