FRANKFURT (Reuters Health) - Germany's Paul Ehrlich Institute said on Monday it would investigate the case of a man reported to have contracted hepatitis A despite having been vaccinated.

The case was first reported in the journal Deutsche Medizinische Wochenschrift by a team of doctors in Bielefeld, led by Prof. Ulrich Junge. On Sunday, Germany's mass circulation Bild newspaper ran a story about the case, bringing it national attention.

The 55-year-old German man was said to have received a full immunization with Twinrix Adult, marketed by GlaxoSmithKline, but some 47 days later became ill after eating shellfish.

Junge and his team concluded that "combined hepatitis A/B vaccination according to the recommended schedule does not guarantee protection in elderly persons."

Dr. Johannes Loewer, head of licensing and inspection at Paul Ehrlich Institute, said in a statement that the agency took Prof. Junge's data seriously and would conduct an investigation. However, he said he currently sees no reason to question the use of Twinrix.

He noted that immunity in people over 40 years old can be less than in people younger than 40. Twinrix Adult was approved in 1996 by the European Agency for the Evaluation of Medicinal Products, and during the approval process it was found to be effective for older people, he said.

Loewer suggested that any older people who have been vaccinated with Twinrix Adult and are nonetheless concerned could be tested to ensure they have effective levels of antibodies against hepatitis A virus.

The Institute said it believed the vaccine to be safe and effective and saw no reason to question its use.

"We are nearly certain that this was not a quality problem," said Susanne Stoecker, spokeswoman at the Institute.