ABSTRACT
The pandemic caused by the novel coronavirus, SARS-CoV-2, first detected in December 2019, resulted in millions of deaths and more than a hundred million confirmed infections in the first 18 months. COVID-19, the disease caused by SARS-CoV-2, is asymptomatic for some, for others it can cause illness ranging from mild flu-like symptoms with the most serious cases manifesting with acute respiratory distress syndrome (ARDS), pneumonia and death. The worldwide effort to develop effective vaccines against COVID-19 and SARS-CoV-2 has been unparalleled throughout history. At the time of writing, there are more than 100 candidate vaccines in clinical development and almost 200 undergoing pre-clinical testing, around the world. These diverse candidates use a range of vaccine strategies and platforms including several relatively novel approaches. Many of these newer strategies have been approved for emergency use and existing data advocate for the critical role that they may have in protecting individuals and reducing the ongoing pandemic. This chapter focusses on nucleic acid and viral vector-based vaccines, currently undergoing post-licensure surveillance, being the most widespread technologies used against the pandemic. As well as reviewing the different vaccine platforms and vaccine candidates, this chapter discusses the events preceding the COVID-19 pandemic that allowed vaccine development to occur at never-before-seen speed, the biological and immunological basis for a SARS-CoV-2 vaccine, the importance of collaborative international efforts and the broad lessons that can be applied towards future pandemics. © 2022 Elsevier Inc. All rights reserved.
ABSTRACT
Background: People living with HIV (PWH) may represent a high-risk group for adverse clinical outcomes from SARS-CoV-2. The duration of protection from SARS-CoV-2 and emerging variants of concern (VOC) infection in PWH following vaccination is unclear. Furthermore, the role of preexisting SARS-CoV-2 immune responses, likely acquired from prior exposure to circulating human coronaviruses (HCoVs), on vaccine-mediated immunity remains to be determined. Understanding the kinetics of immune responses to SARS-CoV-2 and VOCs, and the impact of preexisting SARS-CoV-2 immunity on vaccine-mediated immune responses will be critical in informing COVID-19 vaccination policies in PWH. Methods: In this sub-study of the Phase II/III COV002 trial (open-label, non-randomised clinical trial ID: NCT04400838), 54 HIV+ male participants on antiretroviral therapy (undetectable viral loads, CD4+ T cells >350 cells/ul) and 50 HIV-sex and age-matched controls received two doses of ChAdOx1 nCoV-19 (AZD1222) 4-6 weeks apart and were followed for 6 months. Immune responses to vaccination were determined by ELISA (standard and MSD assay), neutralisation, ACE-2 inhibition, IFNγ ELISpot, activation-induced marker (AIM) assay and T cell proliferation assays. Results: 6 months after vaccination, antibody IgG levels to SARS-CoV-2 S and RBD proteins, ACE-2 inhibition and T cell responses to S protein were significantly higher than baseline (Table 1). Both humoral and cell-mediated immunity waned over time, but with no significant difference compared with HIV-individuals vaccinated with the same regimen. T and B cell-mediated immune responses to VOCs α, β, γ, and δ were detectable, although at lower magnitudes than wild type. Prior exposure to circulating β coronavirus HKU1 and OC43 was associated with measurable proliferative SARS-CoV-2 T cell response at baseline and a higher magnitude of post-vaccine T cell responses. Conclusion: Our data demonstrate no significant difference in ChAdOx1 nCoV-19 vaccine-mediated immune responses by HIV status. For all groups, we show waning but detectable immune responses against SARS-CoV-2 and VOCs 6 months after vaccination supporting the on-going policy to vaccinate against SARS-CoV-2 and reinforces the argument for long-term monitoring of responses.