Respiratory Virus Transmission Network (RVTN)

The Respiratory Virus Transmission Network (RVTN) is designed to estimate whether vaccines reduce transmission of influenza (flu) and COVID-19 within households.

The RVTN uses a case-ascertained household transmission study design. In this study design, households are enrolled by first recruiting a person who tests positive for either influenza or SARS-CoV-2; this person is referred to as an index case. The other members in the household of the index case are then also enrolled.

An index case is eligible for enrollment in this study if they:

• Have tested positive for either influenza or SARS-CoV-2,
• Have not had illness or had their illness for five or fewer days,
• Are likely the first person with illness or infection in the household,
• Live in a non-congregate setting with at least one other person.

Once enrolled, the index case and all enrolled household members answer questions about vaccination history, relevant medical history, demographic information, and ways in which household members interact with one another. They also report daily on illness symptoms for 7–10 days and self-collect respiratory specimens. The specimens collected from the study are tested for influenza or SARS-CoV-2, depending on the infection of the index case. These test results are used to identify more people in the household who are infected and thus help determine the risk of secondary infection within the household. The risk of getting infected from index cases who were vaccinated is compared to the risk of being infected from index cases who were not vaccinated; this comparison is used to assess the vaccine effectiveness (VE) against transmitting infection to household members. This study design is also used to determine the risk of infection for a vaccinated household member compared to the risk for an unvaccinated household member. This is a secondary objective of RVTN.

To carry out the study, the Respiratory Virus Transmission Network has partnered with Westat and Vanderbilt University.

• Westat is recruiting people who have recently tested positive for influenza or SARS-CoV-2 by national commercial laboratories, such as Vault Health. More information about the Track COVID at Home study, conducted by Westat can be found at trackcovidathome.org.
• Vanderbilt University is coordinating with universities and research institutes to recruit people who recently tested positive for influenza or SARS-CoV-2 from outpatient clinics, urgent care clinics, emergency departments, or local testing sites in selected areas of seven states/jurisdictions:

• • Arizona – University of Arizona
  • California – Stanford University
  • Colorado – University of Colorado
  • New York City – Columbia University
  • North Carolina – University of North Carolina
  • Tennessee – Vanderbilt University Medical Center
  •  Wisconsin – Marshfield Clinic Research Institute

Why do we estimate the effectiveness of vaccines against transmitting infection to other people?

While many studies have demonstrated that flu and COVID-19 vaccines protect the person vaccinated against illness and severe disease, vaccination may also reduce the spread of these viruses; a vaccinated person who becomes infected may be less infectious to others. Knowing whether vaccines reduce transmission helps us understand the full benefits of vaccination.