LONDON (Reuters Health) - Britain's Department of Health on Tuesday backed continued use of thimerosal-containing vaccines, saying there was no evidence they harmed children and warning that alternative vaccines without the mercury-based preservative were less effective.

In a statement following calls for older diptheria-tetanus-pertussis (DTP) vaccines to be withdrawn amid fears of autism, the department said recent reviews by the UK Committee on the Safety of Medicines and the US Institute of Medicine had found no evidence that low doses of thimerosal had any effect on childhood development.

"Until an equally effective non-thimerosal-containing DTP vaccine is licensed here, the advice from the Joint Committee on Vaccination and Immunisation is that wholecell DTP--which contains thimerosal--should continue to be used."

Thimerosal has been used for over 60 years to prevent microbial contamination or as an inactivating agent to produce killed vaccines, but parents and some scientists are worried that its use may account at least in part for the rise in reported cases of autism.

Last Friday, it was announced in the US Senate that a provision blocking US lawsuits by families who blame their children's autism on thimerosal would be repealed, paving the way for litigation against manufacturers such as Eli Lilly and Co. who deny liability.

The American development appears to have prompted renewed calls in Britain for a ban on all mercury-containing medicines by pressure groups such as Action Against Autism, who have warned that if the authorities were aware that the old vaccines posed a danger to public health, they could be charged with criminal medical negligence.

In its response, the department said it had been advised by the CSM that there was "no evidence of harm caused by doses of thimerosal in vaccines, except for hypersensitivity reactions."

The statement added: "The view of the (UK) Joint Committee on Vaccination and Immunisation (JCVI) is that the currently available UK licensed DTaP vaccines (which don't contain thimerosal) do not offer the overall protection that DTwP (containing thimerosal) does and thus, having seen all the evidence, JCVI has not recommended as yet a move to routine use of DTaP."

The department noted that vaccine manufacturers were developing research programs to replace or reduce the level of thimerosal used in vaccines in accordance with European guidelines, but said this "may take time because manufacturers are required to ensure that the replacement or elimination of thimerosal does not affect the safety or efficacy of the final vaccine."