Thursday, October 29, 2009

Paracetamol weakens children's response to vacciantion

Paracetamol is sometimes given to infants to reduce their risk of developing fever or a fit caused by fever. In the UK, paracetamol (acetaminophen) is sold over the counter, also present in brands such as Panadol and Calpol. In the US it is more commonly available as Tylenol.

A study published in The Lancet, funded by GlaxoSmithKline Biologicals of Belgium, investigated the effect of giving paracetamol to infants during and immediate after vaccination.

459 healthy infants aged between 9 and 16 weeks were recruited from 10 centres in the Czech Republic and randomised to receive either paracetamol administered every 6 to 8 hrs during the 24 hrs following vaccination or to receive no paracetamol. The parents knew the treatment assigned to their babies.

Researchers found that in both groups, fever above 39.5 degrees C was uncommon, however lower proportion of babies in the paracetamol group had temperature above 38 degrees C. After the primary vaccine doses, more paracetamol doses had to be given to the babies in the control group than the treatment group. They also found that the antibody concentrations following the primary immunisations were significantly lower in the paracetamol group than in the control group and the response varied depending on the vaccination type given.

They concluded that "Although febrile reactions significantly decreased, prophylactic administration of antipyretic drugs at the time of vaccination should not be routinely recommended since antibody responses to several vaccine antigens were reduced."

Critics say this is an important study because there was very few published studies on this issue but further study is needed to demonstrate whether the immunity offered by flu vaccination might be reduced by paracetamol. It may be wise not to give paracetamol routinely to babies as a preventive measure.

Source: "Effect of prophylactic paracetamol administration at time of vaccination on febrile reactions and antibody responses in children: two open-label, randomised controlled trials" The Lancet 2009; 374: 1339-1350 (press release or f/t via Athens)

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