A formal investigation has been launched by French authorities against two managers from drug companies GlaxoSmithKline and Sanofi Pasteur. A second investigation for manslaughter has also been opened against Sanofi Pasteur MSD.

The investigations are in response to allegations that the companies failed to fully disclose side effects from an anti-hepatitis B drug used between 1994 and 1998.

During this time, close to two-thirds of the French population, and almost all newborn babies, received a hepatitis B vaccine. The vaccination campaign was halted after concerns rose over the shot’s side effects.

Thirty plaintiffs, including the families of five people who died after the vaccination, have launched a civil action in the case against the drug companies.