A phase IIb/III, open label, single arm, multi-centre, trial to assess the immunogenicity and safety of an additional dose vaccination with a recombinant protein RBD fusion heterodimer candidate (PHH-1V) against SARS-CoV-2, in adults with pre-existing immunosuppressive conditions vaccinated against COVID-19

Inclusion Criteria:

• Male, female or transgender, ≥ 18 years old at Day 0.
• Provide inform consent form
• Participant who has:
• 3 doses of mRNA vaccines
• 2 doses of mRNA vaccines and previous COVID-19 infection
• 2 doses of Coronavac and 1 Comirnaty, or, 1 Coronavac and 2 Comirnaty
• Participant who has:
• HIV infection with CD4 Tcells counts <400
• Primary antibody deficiency disorders
• Kidney disease on dialysis
• Kidney transplant at least >1 year
• Auto Immune Disease (AID) in treatment with rituximab
• For a female of childbearing potential, to have a negative pregnancy test at Day 0
• Use of any of these contraception:
• Female: hormonal contraception, intrauterine device, vasectomized partner, sexual abstinence, condom.
• Male: Vasectomized participant, sexual abstinence, condom.

Exclusion Criteria:

• History of anaphylaxis to any prior vaccine
• Participants has received or plans to receive live attenuated vaccines, other not live vaccines, or Vaxzevria or Janssen vaccines.
• Pregnant or breast-feeding at Day 0.
• A confirmed COVID-19 diagnose <90 days prior to vaccination day 0.
• A clinically significant acute illness or fever at screening or 48h before day 0.
• Participant had a surgery requiring hospitalisation and has not received the hospital discharge.
• Participant has an ongoing severe and non-stable psychiatric condition
• Participant has a problematic or risky use of substances including alcohol
• Participant has a bleeding disorder that contraindicates intramuscular injection
• Participant suffering from post-acute COVID-19 syndrome / long COVID
• Participant received any immunotherapy to prevent/treat COVID-19 in the last 90 days
• Participant is already participating in another research involving drug, biologics or device
• Participant has donated ≥450 ml of blood products within 12 weeks before screening
• Participant has any medical condition and/or finding that in the investigator opinion might increase participant risk, interfere with the study or impair interpretation of study data.