Influenza vaccine effectiveness in general practice and in hospital patients in Victoria, 2011–2013
The 9th edition of the Immunisation Handbook sponsored by the National Health and Medical Research Council maintained that influenza vaccines were 70%–90% effective in preventing influenza when the match between vaccine strains and circulating strains was good.1 Even when published in 2008, this was probably a generous assessment of the evidence. The 10th edition, published in 2013, maintained that influenza vaccines were 59% effective in preventing influenza in healthy adults and at least as effective in children, although in some years there was no evidence of any benefit.2
Although not explicitly stated in the handbooks, these estimates referred to efficacy in protecting against influenza infections managed in the community, the majority of which are relatively mild. While protection against the mild disease seen in primary care might be modest, it is nevertheless possible that the protection provided against more serious disease, including confirmed influenza infections requiring admission to hospital, might be greater.
In Victoria, two surveillance schemes make it possible to investigate whether there was any major difference in vaccine effectiveness estimates in community and hospital patients. The Victorian Sentinel Practice Influenza Network (VicSPIN) is a group of sentinel general practitioners in Melbourne and regional Victoria, operating since…