Following a plethora of reports one week ago concerning possible adverse events due to vaccines that killed two children in Chiapas, Mexico, the results of an investigation performed by the Mexican Institute for Social Security revealed that bacterial contamination, not linked to the vaccines, were responsible for the tragic fatalities.


The illnesses were reported after 52 children from the rural mining community of La Pimienta were given vaccines May 8 for tuberculosis, rotavirus and Hepatitis B. Unfortunately,  31 of the children “presented adverse reactions presumably associated with the application of these vaccines,” officials said. Two of the children later died.

On May 22, the Mexican Institute for Social Security reported (computer translated) the findings of the investigation into the adverse events. Here are some of their findings:

  • Although no hypothesis is not rejected, the only vaccine given in common to all children affected was that of Hepatitis B, so the research focused on the biological.
  • The batch of the vaccine was properly certified.
  • No adverse events were recorded after 100,000 doses were administered in various parts of the country since Oct. 2014.
  • Results of blood cultures at that time showed the presence of the local external contamination, outside the biological vaccine, in particular bacteria, which was consistent with the clinical pictures of hospitalized children. Microbiology studies conducted on children reported the finding of Staphylococcus hominis, a type of bacterium commonly found in the skin of people. These findings rule out other bacteria, such as those found in the gastrointestinal tract and airways. Molecular studies demonstrated that isolated Staphylococcus hominis in different patients was the same, namely that the bacteria came from a single source of contamination.
  • In conclusion, the Federal Commission for Protection Against Health Risks (COFEPRIS) analysis found that the vaccine was not defective and remained in temperature. Therefore, bacterial contamination occurred during the procedure of handling and application of the vaccine.

On the health of children, as of Friday, 27 children have been discharged from hospital and are in good health. They all returned to their families and their community. The 2 children who are hospitalized are stable.

The Attorney General’s Office will continue investigating the case.