Safety, Effectiveness and Immunogenicity of heterologous mRNA-1273 Boost after Prime with Ad26.COV2.S among Healthcare Workers in South Africa: the single-arm, open-label, Phase 3 SHERPA Study
medrxiv(2024)
Abstract
Given limited data on safety and effectiveness of heterologous COVID-19 vaccine boosting in lower income, high-HIV prevalence settings, we evaluated a mRNA-1273 boost after Ad26.COV2.S priming in South Africa. SHERPA was a single-arm, open-label, phase 3 study nested in the Sisonke implementation trial of 500000 healthcare workers (HCWs). Sisonke participants were offered mRNA-1273 boosters between May and November 2022, a period of circulating Omicron sub-lineages. Adverse events (AE) were self-reported, and co-primary endpoints (SARS-CoV-2 infections and COVID-19 hospitalizations or deaths) were collected through national databases. We used Cox regression models with booster status as time-varying covariate to determine the relative vaccine effectiveness (rVE) of the mRNA-1273 booster among SHERPA versus unboosted Sisonke participants. Of 11248 SHERPA participants in the rVE analysis cohort (79.3% female, median age 41), 45.4% had received one and 54.6% two Ad26.COV2.S doses. Self-reported comorbidities included HIV (18.7%), hypertension (12.9%) and diabetes (4.6%). In multivariable analysis including 413161 unboosted Sisonke participants, rVE of the booster was 59% (95%CI 29-76%) against SARS-CoV-2 infection: 77% (95%CI 9–94%) in the one-Ad26.COV2.S dose group and 52% (95%CI 13-73%) in the two-dose group. Severe COVID-19 was identified in 148 unboosted participants, and only one SHERPA participant with severe HIV-related immunosuppression. Of 11798 participants in the safety analysis, 271 (2.3%) reported a reactogenicity event or unsolicited AE, more among those with prior SARS-CoV-2 infections (adjusted odds ratio [aOR] 2.03, 95%CI 1.59-2.59) and less among people living with HIV (PLWH) (aOR 0.49, 95%CI 0.34-0.69). No related serious AEs were reported. In an immunogenicity sub-study, mRNA-1273 increased antibody functions and T-cell responses 4 weeks after boosting regardless of the number of prior Ad26.COV2.S doses, or HIV status, and generated Omicron spike-specific cross-reactive responses. mRNA-1273 boosters after one or two Ad26.COV2.S doses were well-tolerated, safe and effective against Omicron SARS-CoV-2 infections among HCWs and PLWH.
### Competing Interest Statement
Kate Anteyi, Brett Leav are employees of Moderna, Inc. and may hold stock/stock options in the company. The other authors declare no conflict of interests.
### Clinical Trial
PACTR202310615330649
### Funding Statement
The SHERPA study was funded by Moderna, Inc. (Cambridge, Massachusetts, US) and the South African Medical Research Council (SAMRC). Moderna provided mRNA-1273 free-of-charge. The Sisonke trial was funded by: The National Department of Health through baseline funding to the SAMRC the Solidarity Response Fund NPC The Michael & Susan Dell Foundation the ELMA Vaccines and Immunization Foundation (21-V0001) and the Bill & Melinda Gates Foundation (INV-030342). Moderna representatives reviewed the study protocol, participated in safety oversight, and contributed as manuscript co-authors, but were not involved in data collection and analysis.
### Author Declarations
I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.
Yes
The details of the IRB/oversight body that provided approval or exemption for the research described are given below:
The SHERPA study received full ethical approval by the following ethics committees in South Africa: Pharma-Ethics, Stellenbosch University Health Research Ethics Committee, University of KwaZulu-Natal Biomedical Research Ethics Committee, University of Cape Town Human Research Ethics Committee, Sefako Makgatho University Research Ethics Committee, The South African Medical Research Council Human Research Ethics Committee and the University of the Witwatersrand Human Research Ethics Committee.
I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.
Yes
I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).
Yes
I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.
Yes
Considering this is a clinical trial, universal access to data may not be possible to protect clinical trial participants. However, SHERPA data will be made available by the authors upon reasonable request. You can access the SHERPA data on the following link: https://medat.samrc.ac.za/index.php/catalog/56
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