Phase 2a Trial to Evaluate Safety and Immunogenicity of COVID-19 Vaccine Strategies in HIV-infected/Uninfected Adults.

Inclusion Criteria:

1. . Adult male or female aged 18 and above at the time of written informed consent

2. . Willing and able to give written informed consent

3. . HIV-infected persons on ART for at least three months prior to enrollment, orHIV-uninfected persons

4. . Able to provide evidence of completing a primary COVID-19 vaccination regimen witheither a single dose of Ad26.COV2.S or two doses of BNT162b2 at least two monthsprior to enrolment, or HIV-infected with no prior COVID-19 vaccination and evidenceof prior SAR-CoV-2 infection

5. . Residing in the vicinity of the clinical trial site and planning to remain in thearea of the study for 12months

6. . Able and willing to participate for the duration of the study visits and follow-up

7. . Willing to provide verifiable identification (eg. Identity document, passport) atstudy entry and follow-up visits

Exclusion Criteria:

1. . Positive SARS-CoV-2 PCRor antigen detection test

2. . Persons with undocumented HIV status

3. . HIV-infected persons with CD4count <1 00 cells/mm3and/or Viral Load > 1000copies/ml

4. . Known allergy or history of anaphylaxis or other serious adverse reactions tospecific COVID-19 vaccine constituents

5. . History of capillary leak syndrome, thrombosis with thrombocytopenia syndrome (TTS), heparin-induced thrombocytopenia (HIT), history of any neurological disordersor seizures including Guillain-Barré syndrome, with the exception of febrileseizures during childhood

6. . Participants with acute illness (this does not include minor illnesses such asdiarrhoea or mild upper respiratory tract infection) or body temperature ≥38.0ºC onDay 1 will be excluded from randomization at that time but may be rescheduled forrandomization and/or vaccination at a later date.

7. . Participants who cannot communicate reliably with the investigator

8. . Pregnant or breastfeeding

9. . Women of childbearing potential who are not on an effective long-actingcontraceptive method for at least 21 days prior to enrollment (date of signedinformed consent) and not intending to continue contraception for up to 9 monthspost first vaccination.(See Section 10.5.1 below)

10. . Prior administration of an investigational coronavirus vaccine (for example,SARS-CoV-2, SARS-CoV, Middle East Respiratory Syndrome [MERS-CoV] vaccine), exceptfor participants of the Sisonke trial

11. . Prior administration of any SARS-CoV-2 vaccine boost

12. . Has a medical, psychiatric, or occupational condition that may pose additionalrisk as a result of participation, or that could interfere with safety assessmentsor interpretation of results according to the Investigator's judgment

13. . History of harmful substance or alcohol use within the past 2 years. Thisexclusion does not apply to cannabis use.

14. . Receipt of:

15. . Systemic immunosuppressants or immune-modifying drugs for >14 days in totalwithin 6 months prior to the day of randomization (for corticosteroids, ≥20mg/day prednisone equivalent). Topical tacrolimus is allowed if not used within 14 days prior to the day of randomization. Inhaled, nasal, and topical steroidsare allowed.

16. . Intravenous blood products (red cells, platelets, immunoglobulins, monoclonalantibodies specific for SARS-CoV-2) within 3 months prior to enrollment

17. . Experimental vaccine within the past 6 months before first vaccination

18. . Any inactivated vaccines received within 14 days prior to first vaccinationor planned within 14 days of first vaccination, or live attenuated vaccinesreceived with 30 days prior to the first vaccination or planned within 30 daysof the first vaccination.

19. . Participated in an interventional clinical study within 28 days prior to theScreening Visit (Day 1) or plans to do so while participating in this study.

20. . Employee of the investigator or study site, with direct involvement in theproposed study or other studies under the direction of that investigator or studysite, as well as family members of the employees or the investigator.