Immunisation against influenza was associated with an OR of 0.50 (p = 0.02). Vaccine effectiveness against SCII was therefore 50% (95%CI 12-71%). Effectiveness against SCII with a reported ILI was higher at 73% (95%CI 6-92%; p = 0.04). Other variables were added to the multivariate model, but were found not to be significant at the p < 0.2 level. These were being a doctor; having 7 or more child patient contacts; and being a healthcare worker. Addition of a group-level variance term for recruitment site to the random-effects model was not statistically significant (p(rho = 0) > = 0.498).