COVID-19 Vaccine Candidates and Abortion-Derived Cell Lines - Charlotte Lozier Institute

Accurate information about the development and production of COVID-19 vaccines is essential, especially because many proposed candidates use newer molecular technologies for production of a viral vaccine. One concern regarding the ethical assessment of viral vaccine candidates is the potential use of abortion-derived cell lines in the development, production or testing of a vaccine. This analysis utilizes data from the primary scientific literature when available, along with data from clinical trial documents, reputable vaccine tracking websites, and published commercial information.1 It is the hope that by providing accurate data, recipients can make well-informed decisions regarding vaccine choices.

Analysis of SARS-CoV-2 (COVID-19) Vaccine Candidates *Last Updated 2 June 2021*					DOES NOT USE abortion-derived cell line DOES USE abortion-derived cell line SOME tests DO NOT use abortion-derived cells, SOME DO. � Currently undetermined
Sponsor(s)¹	Country	Strategy²	Clinical Trial Status³	Public Funding⁴	Design & Development	Production	Confirm-atory Lab Tests

WHOLE VIRUS VACCINE – LIVE ATTENUATED or INACTIVATED
Beijing Institute of Biological Products/ Sinopharm	China	Inactivated virus “BBIBP-CorV” Given: Intramuscular 2 doses (3 weeks apart)	WHO granted Emergency Use Listing (EUL) 7May2021 Early approval in China Phase 3 Phase 3		Vero monkey cells Wang et al., Cell 182, P713, 6Aug2020	Vero monkey cells Wang et al., Cell 182, P713, 6Aug2020	Cytopathic test Vero monkey cells Wang et al., Cell 182, P713, 6Aug2020
Wuhan Institute of Biological Products/ Sinopharm	China	Inactivated virus “New Crown COVID-19” Given: Intramuscular 2 doses (3 weeks apart)	Phase 3 Phase 3 Phase 3 Early approval in China Phase 1/2		Vero monkey cells Xia et al., JAMA 324, 951, 13Aug2020	Vero monkey cells Xia et al., JAMA 324, 951, 13Aug2020	Plaque reduction neutralization test Vero monkey cells Xia et al., JAMA 324, 951, 13Aug2020
Bharat Biotech/Indian Council of Medical Research	India	Inactivated virus “BBV152” Given: Intramuscular 2 doses (2 weeks apart)	India EUA granted Phase 3 Phase 3 Phase 1/2 Phase 1/2 Phase 1/2		Vero monkey cells Yadav et al., ResearchSquare 10Sept2020	Vero monkey cells Yadav et al., ResearchSquare 10Sept2020	Antibody ELISA Plaque reduction Vero monkey cellsYadav et al., ResearchSquare 10Sept2020
Institute of Medical Biology, Chinese Academy of Medical Sciences	China	Inactivated virus “SARS-CoV-2 vaccine” Given: Intramuscular 2 doses (2 weeks apart)	Phase 3 Phase 1/2 Phase 1/2		Vero monkey cells Pu et al., medRxiv, 6Oct2020	Vero monkey cells Pu et al., medRxiv, 6Oct2020	Antibody ELISA Neutralizing antibody cytopathic effect Vero monkey cells Pu et al., medRxiv, 6Oct2020 Supplement
John Paul II Medical Research Institute	USA	Live attenuated virus	Pre-clinical		Ethical cell lines as a matter of policy	Perinatal human cells (term umbilical cord and placental)	�
Research Institute for Biological Safety Problems	Kazakhstan	Inactivated virus “QazCovid-in” Given: Intramuscular 2 doses (3 weeks apart)	Phase 3 Phase 1/2		�	�	�
Sinovac Biotech Co., Ltd.	China	Inactivated virus “CoronaVac” Given: Intramuscular 2 doses (2 weeks apart)	WHO granted Emergency Use Listing (EUL) 1June2021 Phase 4 China granted conditional marketing authorization 8Feb2021 Chile, Brazil, Turkey, Indonesia EUA granted Phase 3 Early approval in China Phase 3 Phase 1/2 Phase 1/2 Phase 1/2		Vero monkey cells	Vero monkey cells Gao et al., Science 369, 77, 3July2020	protein test HEK293 cells Supplement Gao et al., Science 369, 77, 3July2020
Valneva and Dynavax	France USA UK	Inactivated Virus “VLA2001” plus adjuvant CpG1018 Given: Intramuscular 2 doses (3 weeks apart)	Phase 3 Phase 1/2		Vero monkey cells	Vero monkey cells Same platform as IXIARO, Valneva press release, 22April2020 Valneva COVID-19 – VLA2001	�

VIRAL VECTOR-BASED VACCINE
Altimmune	USA	Replication-deficient Adenovirus vector “AdCOVID” Given: Intranasal 1-2 doses	Phase 1/2		PER.C6 cells	PER.C6 cells Same platform as NasoVAX NasoVAX uses PER.C6 Licensed PER.C6 from Janssen
AstraZeneca University of Oxford	USA UK	Replication-deficient Adenovirus vector “AZD1222” “ChAdOX1nCoV-19” Given: Intramuscular 2 doses (4 weeks apart)	WHO granted Emergency Use Listing (EUL) on 15Feb2021 UK EUA granted India EUA granted Phase 3 Phase 3 Phase 3 Phase 3 Phase 2/3 Phase 2/3 Phase 1/2 Phase 1/2	Operation Warp Speed HHS-BARDA $1.2 Billion CEPI up to $384 Million	HEK293 cells	HEK293 cells van Doremalen et al., Nature, 30July2020	HEK293 cellsvan Doremalen et al., Nature, 30July2020 MRC-5 cells Almuqrin et al., ResearchSquare 20Oct2020
CanSino Biologics, Inc. Beijing Institute of Biotechnology, Academy of Military Medical Sciences, PLA of China	China	Replication-deficient Adenovirus vector “Ad5-nCoV” Given: Intramuscular 1 dose	EUA in Chile, Hungary, Pakistan, Mexico Phase 3 Phase 3 Phase 2 Phase 2 Phase 2 Phase 1 Phase 1		HEK293 cells	HEK293 cells Biospace, 12May2020
Gamaleya Research Institute	Russia	Replication-deficient Adenovirus vectors (rAd26-S+rAd5-S) “Gam-COVID-Vac” “Sputnik V” Given: Intramuscular 2 doses (3 weeks apart)	Phase 3 Phase 3 EUA in 39 countries as of Mar2021 Early approval in Russia August 2020 Phase 1/2 Phase 1/2		HEK293 cells	HEK293 cells Gamaleya has not published details on this vaccine, but has posted information on use of cell lines for their other adenoviral vaccines
ImmunityBio and NantKwest	USA	Replication-deficient Adenovirus vector recombinant “hAd5 S-Fusion + N-ETSD” Given: Subcutaneous	Phase 1/2 Phase 1/2 Phase 1 Phase 1 Phase 1		E.C7 cells (derivative of HEK293 cells) Rice et al., bioRxiv 30July2020	E.C7 cells (derivative of HEK293 cells) Rice et al., bioRxiv 30July2020	Protein and antibody tests HEK293T cells Rice et al., bioRxiv 30July2020 Seiling et al., medRxiv 6Nov2020
Institut Pasteur and Themis and Merck	USA France	Replication-competent recombinant measles virus “TMV-083” Given: Intramuscular	Development Discontinued Phase 1/2Phase 1	CEPI up to $4.9 Million	HEK293T Development and rescue of recombinant measles virus Hörner et al., PNAS 22Dec2020 Hörner et al. Supplement “SARS-CoV-2 S-encoding vaccine candidates… were generated as described previously”	Vero monkey cells Hörner et al., PNAS 22Dec2020 Hörner et al. Supplement	Lentiviral vectors for antigenic DCFusogenic testHEK293TFusogenic testS protein expressionVero monkey cellsHörner et al., PNAS 22Dec2020 Hörner et al. Supplement
Israel Institute for Biological Research (IIBR)	Israel	Replication-competent recombinant vesicular stomatitis virus (VSVΔG) “IIBR-100” Given: Intramuscular1 dose	Phase 1/2		BHK hamster cells Vero monkey cells Yahalom-Ronen et al., bioRxiv 19June2020	Vero monkey cells Yahalom-Ronen et al., bioRxiv 19June2020	Plaque reduction; immunofluorescence Vero monkey cells Yahalom-Ronen et al., bioRxiv 19June2020
Janssen Research & Development, Inc. Johnson & Johnson	USA	Replication-deficient Adenovirus vector “Ad26.COV2-S” Given: Intramuscular 1 dose (some trials use 2 doses, 8 weeks apart)	FDA Emergency Use Authorization Approved Phase 3 Phase 3 Phase 1/2	Operation Warp Speed HHS-BARDA $1,457,887,081 total	PER.C6 cells	PER.C6 cells Tostanoski et al., Nature Medicine, 3Sept2020; J&J, 30March2020; Janssen Vaccine Technologies
Laboratorio Avi-Mex	Mexico	Live recombinant Newcastle Disease Virus Expressing spike-fusion chimeric protein “Patria” Given: Intramuscular or Intranasal	Phase 1		Bacterial cells BSRT7 hamster cells Per Sun et al., Vaccines 17Dec2020	� Chicken eggs Per Sun et al., Vaccines 17Dec2020	� Neutralization Assay Vero monkey cells Per Sun et al., Vaccines 17Dec2020
Meissa Vaccines, Inc.	USA	Live attenuated recombinant RSV viral vector “MV-014-210” Given: Intranasal 1-3 doses (5 weeks apart)	Phase 1			Vero monkey cells Spike expressing, Based on recombinant RSV platform	�
Rega Institute, KU Leuven	Belgium	Replication-competent attenuated yellow fever vaccine (YF17D) vector “YF-S0” Given: Intramuscular 1 dose	Pre-clinical		BHK-21J hamster cells Sanchez-Felipe et al., Nature, 1Dec2020	BHK-21J hamster cells Sanchez-Felipe et al., Nature, 1Dec2020	Antibody titer Pseudovirus HEK293T cells Immunoblot BHK-21J hamster cells Sanchez-Felipe et al., Nature, 1Dec2020
ReiThera	Italy	Replication-deficient simian adenovirus encoding S “GRAd COV2” Given: Intramuscular 1 dose	Phase 2/3 Phase 1		HEK293T cells Development and rescue of recombinant Capone et al., bioRxiv 22Oct2020	HEK293T cells Capone et al., bioRxiv 22Oct2020	HEK293T cells Capone et al., bioRxiv 22Oct2020
Merck and IAVI	USA	Replication-competent recombinant vesicular stomatitis virus (VSVΔG) “V590” Given: Intramuscular	Development Discontinued Phase 1	Operation Warp Speed HHS-BARDA $38,033,570	Vero monkey cells	Vero monkey cells Use rVSV Ervebo platform Ervebo uses Vero cell culture-11 Description	�
Shenzhen Geno-immune Medical Institute	China	Lentivirus minigenes + Adult human APC (antigen-presenting cells) “COVID-19/aAPC” Given: Subcutaneous 3 doses (2 weeks apart)	Phase 1		�		�
Shenzhen Geno-immune Medical Institute	China	Lentivirus minigenes + Adult human CD/T cells (dendritic cells and T cells) “LV-SMENP-DC” Given: Subcutaneous and Intravenous 1 dose	Phase 1/2		�		�
Vaxart	USA	Replication-deficient Adenovirus vector “VXA-CoV2-1” plus dsRNA adjuvant Given: Oral 2 doses (4 weeks apart)	Phase 1		HEK293 cells	HEK293 cells Moore et al., bioRxiv 6Sept2020
PROTEIN-BASED VACCINE
Anhui Zhifei Longcom Biopharmaceutical/Institute of Microbiology, Chinese Academy of Sciences	China	Protein vaccine Recombinant RBD dimer plus adjuvant ”ZF2001” Given: Intramuscular 2 or 3 doses (28 days apart)	Phase 3 Phase 2 Phase 1/2 Phase 1		HEK293T cells Dai et al., Cell 6Aug2020	CHO hamster cells Dai et al., Cell 6Aug2020	Pseudovirus HEK293T cells Dai et al., Cell 6Aug2020
Clover Biopharmaceuticals, Inc.	China	Protein vaccine “SCB-2019” plus adjuvant CpG 1018 Given: Intramuscular 2 doses (3 weeks apart)	Phase 2/3 Phase 1	CEPI up to $69.5 Million	cDNA in expression vector; transfect CHO hamster cells Liang et al., bioRxiv, 24Sept2020 Trimer-Tag system; Liu et al., Scientific Reports 2017	CHO hamster cells Trimer-Tag system; Liu et al., Scientific Reports 2017	PseudovirusHEK293 cellsRef’d: Nie et al., Emerging Microbes & Infections 24Mar2020Cytopathic effect Vero monkey cellsLiang et al., bioRxiv, 24Sept2020
COVAXX and United Biomedical	USA Taiwan	Protein vaccine “UB-612” S1-RBD-protein; Multitope Peptide-Based Vaccine (MVP) Given: Intramuscular 2 doses (4 weeks apart)	Phase 2/3 Phase 1		cDNA in expression vector; transfect CHO hamster cells Guirakhoo et al., bioRxiv, 30Nov2020	CHO hamster cells Guirakhoo et al., bioRxiv, 30Nov2020	Antibody blocked binding to hACE2 HEK293 Guirakhoo et al., bioRxiv, 30Nov2020
Federal Budgetary Research Institution State Research Center of Virology and Biotechnology “Vektor”	Russia	Protein vaccine “EpiVacCorona” chemically synthesized peptide antigens of SARS-CoV-2, conjugated to a carrier protein adsorbed on an aluminum-containing adjuvant Given: Intramuscular2 doses (3 weeks apart)	Phase 3 Early approval in Russia Oct 2020 Phase 1/2		�	chemically synthesized peptide antigens	�
Instituto Finlay de Vacunas	Cuba	Protein vaccine “Finlay-FR-1” (“Soberana 01”) Receptor-binding domain (RBD) SARS-CoV-2 spike + adjuvant Given: Intramuscular2 doses (4 weeks apart)	Phase 1/2 Phase 1		� RBD produced in mammalian cells Garcia-Rivera, MEDICC Review, 30Oct2020	� RBD produced in mammalian cells Garcia-Rivera, MEDICC Review, 30Oct2020	�
Instituto Finlay de Vacunas	Cuba	Protein vaccine “Finlay-FR-2” (“Soberana 02”) Receptor-binding domain (RBD) SARS-CoV-2 spike chemically bound tetanus toxoid + adjuvant Given: Intramuscular2 doses (4 weeks apart)	Phase 2 Phase 1		� RBD produced in mammalian cells Garcia-Rivera, MEDICC Review, 30Oct2020	� RBD produced in mammalian cells Garcia-Rivera, MEDICC Review, 30Oct2020	�
John Paul II Medical Research Institute	USA	Recombinant Protein Perinatal human cells (term umbilical cord and placental)	Pre-clinical		Ethical cell lines as a matter of policy	Perinatal human cells (term umbilical cord and placental)	�
Kentucky BioProcessing, Inc. (British American Tobacco)	USA	Protein vaccine “KBP-201” Plant-expressed RBD Given: Intramuscular2 doses (3 weeks apart)	Phase 1/2		Recombinant DNA sequence for RBD of SARS-CoV-2	Plant expression of RBD peptide	�
Medicago	Canada	Protein on Virus-Like Particle “CoVLP” Plant-expressed spike protein particle with adjuvant, CpG1018 or AS03 Given: Intramuscular 2 doses (3 weeks apart)	Phase 2/3 Phase 2 Phase 1		Recombinant DNA sequence in Agrobacterium, transformation of plant cells	Plant expression of protein and VLP Ward et al., medRxiv 6Nov2020	Pseudovirus HEK293 cells Ward et al., medRxiv 6Nov2020
Migal Galilee Research Institute	Israel	Protein vaccine E. coli expressed chimeric S and N proteins Given: Oral	Pre-clinical		�	Bacterial production system MigVax’s corona subunit vaccine	�
Novavax	USA	Protein vaccine “NVX-CoV2373” Baculovirus expression plus Matrix M adjuvant Given: Intramuscular 2 doses (3 weeks apart)	Phase 3 Phase 3 Phase 2 Phase 1	Operation Warp Speed HHS-BARDA $1,600,434,523 CEPI up to $388 Million		Sf9 insect cells Bangaru et al., Science, 27Nov2020 Bangaru et al., Supplement Bangaru et al., bioRxiv preprint, 6Aug2020; Graphical view	Pseudovirus HEK293 cells Bangaru et al., Science, 27Nov2020 Bangaru et al., Supplement Bangaru et al., bioRxiv preprint, 6Aug2020
Sanofi and GSK Protein Sciences	USA France	Protein vaccine Baculovirus expression plus AS03 adjuvant Given: Intramuscular 2 doses (3 weeks apart)	Phase 3 Phase 2 Phase 1/2	Operation Warp Speed HHS-BARDA $2,072,775,336 total	Recombinant baculovirus Francica et al., bioRxiv 2Mar2021	Sf9 insect cells Francica et al., bioRxiv 2Mar2021 Baculovirus expressed recombinant protein	Pseudovirus HEK293T cells Francica et al., bioRxiv 2Mar2021
Sorrento	USA	Protein vaccine “T-VIVA-19” SARS-Cov-2 spike protein S1 domain fused with human IgG-Fc Given: Intramuscular	Pre-clinical			CHO cells Herrmann et al., bioRxiv preprint, 30June2020	Antibody ELISA; Neutralization assays Vero monkey cells Herrmann et al., bioRxiv preprint, 30June2020
Sorrento	USA	Protein vaccine “STI-6991” SARS-Cov-2 spike protein expressed on K562 cells	Pre-clinical		�	K562 cells Concept: Ji et al., Medicine in Drug Discovery March2020	�
University of Pittsburgh	USA	Protein vaccine Adenovirus-expressed recombinant proteins “PittCoVacc” Given: Microneedle arrays	Pre-clinical		HEK293 cells	HEK293 cells Kim et al., EBioMedicine , 2April2020
University of Queensland and CSL Ltd.	Australia	Protein vaccine “V451” Recombinant protein with proprietary molecular clamp Given: Intramuscular	HALTED Phase 1 Phase 1 Phase 1	CEPI up to $4.5 Million		expiCHO hamster cells	�
Walter Reed Army Institute of Research (WRAIR) / U.S. Army Medical Research and Development Command	USA	Protein vaccine ”SpFN” Spike-Ferritin nanoparticle with ALFQ adjuvant Given: Intramuscular 2-3 doses (4 weeks apart; plus 6 months after initial injection)	Phase 1		Expi293 cells Carmen et al., bioRxiv 28April2021	Expi293 cells Carmen et al., bioRxiv 28April2021	Pseudovirus HEK293 cells Virus neutralization Vero monkey cells Joyce et al., bioRxiv 25Mar2021 & Supplement

RNA VACCINE
Arcturus Therapeutics	USA	mRNA vaccine self-transcribing, replicating “LUNAR-CoV19” (“ARCT-021”) in vitro transcription reaction with T7 RNA polymerase from STARR plasmid template LUNAR proprietary lipid nanoparticle encapsulated Given: Intramuscular 1 dose	Phase 2 Phase 2 Phase 1/2		Sequence designed on computer	No cells used de Alwis et al., bioRxiv 3Sept2020	protein test HEK293 Protein expression Hep3b cells Plaque reduction neutralization Vero monkey cells de Alwis et al., bioRxiv 3Sept2020
CureVac	Germany	mRNA vaccine non-replicating “CVnCoV” in vitro transcription lipid nanoparticle encapsulated Given: Intramuscular 2 doses (4 weeks apart)	Phase 3 Phase 2/3 Phase 2 Phase 1	CEPI up to $15.3 Million	Sequence designed on computer	No cells used Rauch et al., bioRxiv 9Feb2021	Protein test Reticulocyte lysate, HeLa cells Rauch et al., bioRxiv 9Feb2021
Imperial College London	UK	mRNA vaccine Self-amplifying ”LNP-nCoVsaRNA” in vitro transcription lipid nanoparticle encapsulated Given: Intramuscular 2 doses	Phase 1		Expression plasmid HEK293 cells McKay et al., bioRxiv 25April2021	No cells used McKay et al., bioRxiv 25April2021	Pseudovirus HEK293T cells McKay et al., bioRxiv 25April2021
Moderna, Inc. with National Institutes of Health	USA	mRNA vaccine non-replicating “mRNA-1273” T7 RNA polymerase-mediated transcription from DNA plasmid template LNP (lipid nanoparticle) encapsulated Given: Intramuscular 2 doses (4 weeks apart)	*FDA Emergency Use Authorization Approved* Phase 3 Phase 2 Phase 1	Operation Warp Speed HHS-BARDA $2,479,894,979 total CEPI up to $1 Million	Sequence designed on computer	No cells used Corbett et al., Nature , 5Aug2020	protein test & pseudovirus HEK293 cells Plaque reduction neutralization Vero monkey cells Corbett et al., Nature , 5Aug2020
Pfizer and BioNTech	USA Germany	mRNA vaccine non-replicating “BNT-162a1,b1,b2,b3,c2” nucleoside-modified mRNA in vitro transcribed by T7 polymerase from a plasmid DNA template LNP (lipid nanoparticle) encapsulated Given: Intramuscular 2 doses (3 weeks apart)	*FDA Emergency Use Authorization Approved* UK EUA granted Phase 2/3 Phase 1/2 Phase 1/2 Phase 1 Phase 1	Operation Warp Speed HHS-BARDA $1.95 Billion	Sequence designed on computer	No cells used Vogel et al., bioRxiv 8Sept2020	protein test & pseudovirus HEK293 cells Neutralization assay Vero monkey cells Vogel et al., bioRxiv 8Sept2020
Providence Therapeutics	Canada	mRNA vaccine “PTX-COVID19-B” mRNA in vitro transcription from plasmid template using T7 RNA polymerase LNP (lipid nanoparticle) encapsulated Given: Intramuscular 2 doses (4 weeks apart)	Phase 1		HEK293T cells used to select mRNA candidate Liu et al., bioRxiv 12May2021	No cells used Cision, 5Aug2020 Providence Therapeutics Liu et al., bioRxiv 12May2021	Pseudovirus, serum neutralization HEK293T cells Vero monkey cells Liu et al., bioRxiv 12May2021
Sanofi Pasteur and Translate Bio	USA France	mRNA vaccine non-replicating “MRT5500” synthesized by in vitro transcription employing RNA polymerase with a plasmid DNA template LNP (lipid nanoparticle) encapsulated Given: Intramuscular 2 doses (3 weeks apart)	Phase 1/2		HEK293T cells used to select mRNA candidate Kalnin et al., npj Vaccines 19Apr2021	No cells used Kalnin et al., npj Vaccines 19Apr2021 Kalnin et al., bioRxiv 14Oct2020 mRNA production in the lab ; Translate Bio scientific platform	protein test & pseudovirus HEK293 cells Kalnin et al., npj Vaccines 19Apr2021 Kalnin et al., bioRxiv 14Oct2020

DNA VACCINE
Genexine	Korea	DNA vaccine “GX-19” DNA synthesized in vitro, placed in plasmid vector Given: Intramuscular and Electroporation 2 doses (4 weeks apart)	Phase 1/2 Phase 1/2		Sequence designed on computer	No cells used Seo et al., Vaccines 24March2021	No cells used Seo et al., Vaccines 24March2021
Inovio Pharmaceuticals	USA	DNA vaccine “INO-4800” DNA synthesized in vitro, placed in plasmid vector Given: Intradermal Electroporation 2 doses (4 weeks apart)	Phase 2/3 Phase 2 Phase 1/2 Phase 1	Operation Warp Speed CEPI up to $22.5 Million	Sequence designed on computer	No cells used Smith et al., Nature 20May2020	protein test & pseudovirus HEK293 cells Smith et al., Nature 20May2020
Osaka University, AnGes, Takara Bio	Japan	DNA vaccine “AG0301-COVID19” “AG0302-COVID19” Chemically synthesized plasmid vector grown in E. coli Pressure injector Given: Intramuscular 2 doses (2 weeks apart)	Phase 2/3 Phase 1/2 Phase 1/2		Sequence designed on computer	No cells used E. coli</em Nishikawa et al., bioRxiv, 14Jan2021	Virus neutralization Vero E6 cells monkey cells Nishikawa et al., bioRxiv, 14Jan2021
Symvivo Corporation	Canada	DNA vaccine “bacTRL-spike” Genetically engineered Bifidobacterium longum Given: Oral, bacteria bind to gut lining 1 dose	Phase 1		�	No cells used	�
Zydus Cadila	India	DNA vaccine “ZyCov-D” Chemically synthesized plasmid vector grown in E. coli Given: Intramuscular 3 doses (4 weeks apart)	Phase 3 Phase 1/2		Sequence designed on computer	No eukaryotic cells used E. coli</em Dey et al., bioRxiv, 26Jan2021	Expression analysis Plaque reduction Vero cells monkey cells Dey et al., bioRxiv, 26Jan2021 Yadav et al., bioRxiv, 3Feb2021

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