Japan's Ministry of Health, Labour and Welfare has temporarily suspended use of Pfizer's Prevnar and Sanofi-Aventis' ActHIB while it investigates the deaths of four children linked to the paediatric vaccines.

The children, whose ages range between six months and two years old, died after being given either Prevnar for protection against meningitis and pneumonia, ActHIB (for Haemophilus influenzae type b) or a combination of several paediatric vaccines, the ministry said. The suspension will remain in place until a safety panel, which meets tomorrow, has reported on the cases.

A Pfizer spokeswoman told Dow Jones that the firm "thoroughly evaluates all reported cases and works closely with health authorities to determine if there is any association with use of our medicines and vaccines". She noted that the MHLW has posed a number of questions to Pfizer, which is in the process of preparing responses to those inquiries, adding that based on the company's evaluation, the Prevnar doses administered in the four cases were from three separate lots.

Victor Carey, Asia Pacific medical director for Sanofi’s vaccines unit, told Bloomberg that “no causal relationship has been established between immunisation and these fatalities, but an investigation is under way, which we’re fully cooperating with". He added that about 1.5 million Japanese children have received ActHIB since it was approved in Japan in 2007.