Table 2.

TLR agonists as vaccine adjuvants in SARS-CoV-2 vaccines.

Vaccine name	Sponsor/company	TLR agonist adjuvant	Target TLR	Clinical phase	Disease target	Effects on host immunity	Clinical Trials. Gov identifier/reference
SCB-2019	-	CpG-1018	TLR9	Phase II/III	COVID-19	Provides notable protection against all circulating delta, gamma and mu variants of SARS-CoV-2	Bravo et al. (2022)
SCB-2019 Recombinant SARS-CoV-2 Trimeric S-protein Subunit Vaccine	Zhejiang Clover Biopharmaceuticals, Inc.	CpG 1,018/Alum-adjuvanted	TLR9	Phase II	COVID-19	Results yet to be published	NCT04954131
CoVac-1 (COVID-19 peptide vaccine)	The University Hospital Tübingen	TLR 1/2 agonist XS15	TLR 1/2	Phase I	COVID-19	CoVac-1-induces IFN-γ T cell responses; induces broad, potent and variant of concern-independent T cell responses	Heitmann et al. (2022)
SARS-CoV-2 subunit vaccine	Georgia Institute of Technology, USA	MPLA	TLR4	Phase I	COVID-19	In mice model, MPLA+PUUC NPs enhanced CD4+ CD44+ activated memory T cell responses against spike protein in the lungs while MPLA NPs increased anti-spike IgA in the bronchoalveolar fluid and IgG in the blood	Atalis et al. (2022)
TLR7-NP adjuvanted SARS-CoV-2 vaccine	Stanford University, USA	Toll-like receptor 7 agonist nanoparticle (TLR7-NP)	TLR7	Phase I	COVID-19	Induces cross-reactive Abs for both dominant and subdominant epitopes and antigen-specific CD8+ T-cell responses in mice	Yin et al. (2023)