Evaluation of the Effectiveness of Vaccination With 2009 H1N1 Vaccines During Influenza Season 2010-11

Inclusion criteria for the interview follow-up: * Participating in the study "Evaluation of a vaccination campaign with A(H1N1)v pandemic vaccines: a prospective cohort study" (AH1N1-483-09THL) * Assigned to use the services of Tampere health care centre; * Written consent for the interview follow-up phase obtained by mail; * Able to adhere to all protocol-required study procedures without any special burden or risk, as judged by the participant himself/herself Inclusion criteria for the confirmation of 2009 H1N1 influenza cases: * Participating in the study interview follow-up of the current study 'Evaluation the effectiveness of vaccination with 2009 H1N1 vaccines during influenza season 2010-11 (H1N1-495-10THL) * Assigned to use the services of Tampere health care centre * Written informed consent for the confirmation phase obtained at the first study visit * Able to adhere to all protocol required study procedures without any special burden or risk, as judged by the investigator or designate Exclusion criteria: * No specific exclusion criteria will be applied