Possible cause identified for 2010 flu vaccine adverse events

Assoc Prof Heath Kelly, Head of the Epidemiology Unit at the Victorian Infectious Diseases Reference Laboratory, and co-authors write that CSL is one of only a few manufacturers around the world to use deoxycholate as a splitting agent in its influenza vaccines.

The authors point out that use of deoxycholate in the manufacture of influenza vaccines was a common factor in previous clusters of adverse events following immunisation (AEFI) elsewhere in the past 15 years, including Canada and Europe. 

“In Canada, a novel adverse event – designated oculorespiratory syndrome (ORS) – was identified during the 2000-2001 influenza immunisation campaign in association with a domestically manufactured split-virus TIV,” the authors said. This adverse event was first recognised by a group of investigators that included one of the article’s co-authors, Dr Danuta Skowronski.

“Of 960 reported ORS cases, 96 per cent of the 937 cases where the administered vaccine brand was known followed receipt of a domestically produced deoxycholate-split TIV, while only one per cent was reported following receipt of an imported TIV that used Triton X-100 as the splitting agent,” the authors said.

“Inadequate virus splitting was considered a likely factor in the Canadian ORS cluster and investigations revealed a similar experience at least five years earlier in several European countries.”

Prof Kelly said that, in June this year, the US Food and Drug Administration (FDA) issued a warning to CSL over the manufacturer’s splitting procedure, stating that CSL “failed to determine optimal splitting conditions for new virus strains before the strains deficient”.

“These concerns, together with the previous Canadian and European experiences, suggest that incompletely split virus, and perhaps other factors related to the use of deoxycholate, provide a plausible explanation of the AEFI associated with the 2010 CSL TIV,” the authors concluded.

“Immunisation is important in preventing serious illness due to influenza and understanding the cause of AEFI clusters such as these is critical to maintain public trust and acceptance of recommended vaccines.”

The Medical Journal of Australia is a publication of the Australian Medical Association.

The statements or opinions that are expressed in the MJA  reflect the views of the authors and do not represent the official policy of the AMA unless that is so stated.

CONTACT:             A/Prof Heath Kelly                      0437 098 423 / 03 9342 2608
                           heath.kelly@mh.org.au

                           Dr Danuta Skowronski                  Danuta.Skowronski@bccdc.ca