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, or hiv-uninfected persons 4. . able to provide evidence of completing a primary covid-19 vaccination regimen with either a single dose of ad26.cov2.s or two doses of bnt162b2 at least two months prior to enrolment, or hiv-infected with no prior covid-19 vaccination and evidence of prior sar-cov-2 infection 5. . residing in the vicinity of the clinical trial site and planning to remain in the area 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) at study entry and follow-up visits

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, or hiv-uninfected persons 4. . able to provide evidence of completing a primary covid-19 vaccination regimen with either a single dose of ad26.cov2.s or two doses of bnt162b2 at least two months prior to enrolment, or hiv-infected with no prior covid-19 vaccination and evidence of prior sar-cov-2 infection 5. . residing in the vicinity of the clinical trial site and planning to remain in the area 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) at study entry and follow-up visits

inclusion criteria: . adult male or female aged 18 and above at the time of written informed consent . willing and able to give written informed consent . hiv-infected persons on art for at least three months prior to enrollment, or hiv-uninfected persons . able to provide evidence of completing a primary covid-19 vaccination regimen with either a single dose of ad26.cov2.s or two doses of bnt162b2 at least two months prior to enrolment, or hiv-infected with no prior covid-19 vaccination and evidence of prior sar-cov-2 infection . residing in the vicinity of the clinical trial site and planning to remain in the area of the study for 12months . able and willing to participate for the duration of the study visits and follow-up . willing to provide verifiable identification (eg. identity document, passport) at study entry and follow-up visits

inclusion criteria: . adult male or female aged 18 and above at the time of written informed consent . willing and able to give written informed consent . hiv-infected persons on art for at least three months prior to enrollment, or hiv-uninfected persons . able to provide evidence of completing a primary covid-19 vaccination regimen with either a single dose of ad26.cov2.s or two doses of bnt162b2 at least two months prior to enrolment, or hiv-infected with no prior covid-19 vaccination and evidence of prior sar-cov-2 infection . residing in the vicinity of the clinical trial site and planning to remain in the area of the study for 12months . able and willing to participate for the duration of the study visits and follow-up . willing to provide verifiable identification (eg. identity document, passport) at study entry and follow-up visits