A cohort of 4000 community-dwelling adults is followed to evaluate the effectiveness of the Finnish national A(H1N1)v influenza vaccination campaign in preventing the first episode of laboratory-confirmed A(H1N1)v influenza. The safety of vaccination and the severity of the disease are followed primarily from health care registers. In a subgroup of 200 participants, the humoral and cellular immunogenicity of the vaccine will be studied.

Inclusion Criteria:

• Full legal competence;
• Written informed consent obtained;
• Assigned to use the services of Tampere health centre and community-dwelling;
• At least 18 and no more than 75 years old, inclusive;
• Belongs to the target group of A(H1N1)v vaccination in the region during the pandemic vaccination campaign;
• Able to communicate fluently in Finnish or Swedish
• Able to adhere to all protocol required study procedures without any special burden or risk, as judged by the investigator or designate.

Exclusion Criteria:

• For the total study cohort, no specific exclusion criteria will be applied;

• For the subgroup for follow-up of immunogenicity of the vaccine (immunogenicity cohort), exclusion criteria comprise:

  • previous severe allergic reaction to influenza vaccines or known severe allergy to the ingredients of the vaccine
  • previous severe allergic reaction to eggs
  • significant immunological disorder

The subjects will be invited from the population assigned to use the services of Tampere health centre, according to the target groups for pandemic vaccination. Invitations will be distributed at the maternity clinics for pregnant women, at work places for health professionals, and letters will be sent home to random sample of subjects at age groups of 18-24 years, 25-64 years and potetially later at 65-75 years of age.