The primary objective of this study is to determine the incidence of severe RSV LRTI requiring hospitalization among infants born < 35 weeks gestational age for one year of follow-up.

This is an epidemiologic study of the incidence of severe RSV LRTI among Brazilian children born <35WGA. The study will enroll competitively 350 subjects from 3 sites in Brazil. Preterm children will be identified after birth and up to 72 hours after hospital discharge and followed for one year after the enrollment. Subjects will be seen monthly for the first 6 months and bimonthly until one year of follow-up. At each visit, a medical and social history will be updated and a physical examination will be performed. Legal representative will notify study personnel in the event of a respiratory illness or hospital admission at which time the subject will be seen by an investigator. Children with LRTI diagnosed by physical examination will have viral diagnostic tests performed. Subjects with a LRTI not requiring hospitalization will be followed by telephone weekly until illness resolution. Hospitalized children with a LRTI will be followed daily while hospitalized and followed by telephone until illness resolution. All medical interventions and outcomes will be recorded.

Inclusion Criteria:

• Male and female infants that were born <35 weeks gestational age

• The inclusion must be done during the following period:

  • 24 hours prior confirmed maternity hospital discharge date, or
  • Up to 72 hours after documented maternity hospital discharge date. In this case, RSV rapid test must be performed and subjects should be enrolled only if the results is negative.

• Less than 6 months of age at screening

• Born into or transferred to a participating hospital

• Able to receive follow-up medical care at the participating site and provide information during the follow-up period

• The legal representative is capable of understanding and complying with parameters as outlined in the protocol and able and willing to participate in this study, by signing the informed consent approved by an Independent Ethics Committee (IEC)/Institutional Review Board (IRB), after all the aspects of the study that might be relevant for his/her decision to participate are explained and all his/her questions and doubts are elucidated, and prior to the initiation of any screening or study-specific procedures.

Exclusion Criteria:

• RSV infection prior inclusion.
• Receipt of palivizumab or other immunoglobulin preparation containing RSV specific antibodies (i.e. RSV hyperimmunoglobulin, polyclonal intravenous immunoglobulin, cytomegalovirus hyperimmunoglobulin, varicella-zoster hyperimmunoglobulin)

Infants < 35 wGA born into or transferred to a participating hospital meeting all of the inclusion criteria and none of the exclusion criteria specified in the protocol will be selected to participate. Subjects will be identified in the NICU or newborn nursery and enrolled in the study 24 hours prior to confirmed hospital discharge or up to 72 hours after maternity hospital discharge date.