The PRIMAKid trial is a general practice based double-blind randomized placebo-controlled trial on the effectiveness and costs of combined influenza and pneumococcal vaccination in pre-school children with recurrent respiratory tract infections. A target number of 660 children aged 18-72 months with a history of two or more general practitioner attended episodes of RTI, are included. Exclusion criteria are diseases accompanied by a high risk of recurrent RTI and conditions chronically treated with corticosteroids. Over a period of 7 to 22 months follow-up, the number of febrile RTI-episodes as primary outcome is assessed, and as secondary outcomes the severity and length of febrile RTI-episodes, medical visits / interventions, health-related quality of life and productivity loss of parents.

Inclusion Criteria:

• Age between 18-72 months
• A history of two or more episodes of general practitioner attended RTIs

Exclusion Criteria:

• No intention to move within 12 months to another region
• Provision of informed consent
• Good mastering of the Dutch language
• Absence of chronic diseases such as asthma treated with corticosteroids or high-risk disease (such as palatoschisis, Down syndrome, cystic fibrosis, etc.)
• No previous influenza vaccination or pneumococcal vaccination or Hepatitis B vaccination
• No hypersensitivity to eggs and/or antibiotics, and/or serious history of serious adverse events through vaccination