for people ages 18 years and up (full criteria)
study started
estimated completion



In this Phase 4, open-label trial, participants of the ACTIV-3/TICO clinical trial (NCT04501978) at selected study sites who receive certain pre-specified, blinded investigational agents or placebo as part of that trial and who have since achieved sustained recovery from COVID-19 and meet certain criteria, including not having received a COVID-19 vaccination since enrollment, will be randomized to one of four groups to receive the Moderna mRNA-1273 or the Pfizer BNT162b2 vaccine (mRNA vaccines). No "dummy/placebo" vaccine will be used. Choice of Moderna or Pfizer vaccine is determined based on availability at the site. The choice is individual, although participants vaccinated twice should receive the same type of vaccine when receiving two injections. The study's objective is to evaluate if the vaccine is best administered early or deferred after recovery, and whether one injection provides comparable immune response to a two injection course of vaccination. Participants will remain blinded to the interventions received in the ACTIV-3/TICO study, however allocation to the timing of vaccination and to one or two vaccinations in this (VATICO) study is not blinded.

Official Title

SARS-CoV-2 Vaccination Strategies in Previously Hospitalized and Recovered COVID-19 Patients


Participants from the ACTIV-3/TICO clinical trial must still be blinded and be within 28 to 90 days after their initial TICO randomization. They will be randomized as part of a 2x2 factorial design to one of four groups: (i) Immediate versus 12 week deferral of first dose administration, and also (ii) One dose only, versus two doses to be given 4 weeks apart. The primary objectives of this study are: (i) To estimate the difference in neutralizing antibody (NAb) response to the mRNA vaccine from baseline to Week 48 among participants vaccinated early versus deferred, and (ii) To estimate the difference in NAb response to this vaccine among participants vaccinated once versus twice. A key secondary objective is to ascertain the effect, if any, of SARS-CoV-2 monoclonal antibodies, and other interventions that have been studied in hospitalized COVID-19 subjects, on natural and vaccine-induced immunity. Participants will be offered enrollment between 28 and 90 days after receiving select ACTIV-3/TICO investigational agents or placebo. Participants will have blood collected at time of enrollment, and at Weeks 12, 24 and 48 after study entry. Approximately 640 participants will be recruited. The total sample size will depend on how many investigational agents/placebo are evaluated in ACTIV-3/TICO.


Covid19 COVID-19 COVID 19 Coronaviridae Infections Coronavirus Infections RNA Virus Infections Virus Diseases Nidovirales Infections SARS-CoV-2 SARS Coronavirus VATICO ACTIV-3 ACTIV3 TICO Vaccines Moderna mRNA-1273 COVID-19 vaccine Pfizer BNT162b2 COVID-19 vaccine


You can join if…

Open to people ages 18 years and up

  • Participating in (ACTIV-3) TICO trial and received a selected blinded investigational agent, or placebo for that agent, at selected sites.
  • Willingness to strictly adhere to the randomly allocated dosage number and schedule for vaccine administration.
  • Participant is between Day 28 and Day 90 TICO visits inclusive at time of randomization.
  • At time of screening for this study, has experienced sustained recovery for at least two consecutive weeks, i.e. having return uninterrupted to the person's premorbid living facility (or equivalent) for at least 2 consecutive weeks.
  • Ability and willingness of participant (or legally authorized representative) to provide informed consent prior to initiation of any study procedures.

You CAN'T join if...

  • Receipt of a SARS-CoV-2 (COVID-19) vaccine after enrollment into TICO. Participants who received a SARS-CoV-2 vaccine prior to enrollment in TICO may be enrolled in this study.
  • Known allergy to any component of the study eligible vaccine(s).


  • Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center (Site 066-002), 1124 W. Carson St., CDCRC
    Torrance California 90502 United States
  • San Francisco VAMC (Site 074-002), 4150 Clement Street
    San Francisco California 94121 United States
  • Cedars-Sinai Medical Center (Site 208-002), 8700 Beverly Blvd
    Los Angeles California 90048 United States
  • Stanford University Hospitals & Clinics (Site 203-003), Stanford University, School of Medicine, 300 Pasteur Dr., Grant Bldg, Room S011
    Stanford California 94305 United States


in progress, not accepting new patients
Start Date
Completion Date
International Network for Strategic Initiatives in Global HIV Trials (INSIGHT)
FDA Safety Alerts and Recalls CDC (Centers for Disease Control and Prevention): Coronavirus (COVID-19) website A Participant's Guide to Clinical Trials (NIAID) Find a Clinical Trial Clinical Trials at NIAID National Institute for Allergy and Infectious Diseases (NIAID) NIH COVID-19 treatment guidelines WHO COVID-19 treatment guidelines
Phase 4 COVID-19 Research Study
Study Type
Expecting 640 study participants
Last Updated