REAGENT or RESOURCE	SOURCE	IDENTIFIER
Antibodies
Purified NA/LE mouse anti-human CD28 (clone 28.2)	BD Pharmingen	Cat# 555725; RRID:AB_2130052
Purified NA/LE mouse anti-human CD49d (clone L25)	BD Pharmingen	Cat# 555501; RRID:AB_396068
CD4 ECD (clone SFCI12T4D11)	Beckman Coulter	Cat# 6604727; RRID:AB_394488
CD8 BV510 (clone RPA-8)	Biolegend	Cat# 301048; RRID:AB_2561942
CD3 BV650 (clone OKT3)	Biolegend	Cat# 317324; RRID:AB_2563352
IFN-g AlexaFluor® 700 (clone B27)	BD Biosciences	Cat# 557995; RRID:AB_396977
TNF-a BV786 (clone Mab11)	Biolegend	Cat# 502948; RRID:AB_2565858
IL-2 APC (clone MQ1-17H12)	Biolegend	Cat# 500310; RRID:AB_315097
Anti-human IgG (Fab-specific)-horseradish peroxidase	Sigma Aldrich	Cat# A0170; RRID:AB_257868
Biological samples
Unvaccinated children blood samples	Red Cross War Memorial Children’s Hospital	https://www.childrenshospitaltrust.org.za/the-hospital/
Unvaccinated children blood samples	Mbekweni and TC Newman clinics	https://www.westerncape.gov.za/facility/mbekweni-community-day-centre-cdc https://www.westerncape.gov.za/facility/tc-newman-community-day-centre-cdc
Convalescent health care worker blood samples	Groote Schuur Hospital	https://www.gsh.co.za
Chemicals, peptides, and recombinant proteins
Brefeldin A	Sigma Aldrich	Cat# B7651-5MG
PepTivator® SARS-CoV-2 Prot_S	Miltenyi Biotech	Cat # 130-126-701
Peptide Array, SARS-Related Coronavirus 2 Nucleocapsid (N) Protein	BEI resources	Cat# 52404
Peptide Array, SARS-Related Coronavirus 2 Membrane (M) Protein	BEI resources	Cat# 52403
PtX™ SARS-CoV-2 Spike Protein (S1, Rabbit FC)	Cape Bio Pharms (Pty) Ltd	Cat# CB_0002.2
Recombinant SARS-CoV-2 Spike RBD His-tag (HEK293 Expressed)	Bio-Techne	Cat#10500-CV
BTA SARS-CoV-2 Nucleocapsid (1mg)	BioTech Africa	Cat# BA25-C
Recombinant HCoV-HKU1 spike (HEK293F Expressed)	In-house	N/A
Recombinant HCoV-OC43 spike (HEK293F Expressed)	In-house	N/A
O-phenylenediamine dihydrochloride (OPD), Sigmafast TM	Sigma Aldrich	P9187-50SET
3′,5,5′-Tetramethylbenzidine (TMB) substrate	Thermofisher Scientific	Cat# 34029
Casein, Hammarsten Bovine	Sigma Aldrich	E0789-500
Phosphate buffered saline with 0.05% tween, pH 7.4	Sigma Aldrich	P3563-10PAK
Critical commercial assays
BD FACS™ Lysing Solution	BD Biosciences	Cat # 349202
BD Perm/Wash Buffer	BD Biosciences	Cat# 554723
CellFIX buffer	BD Biosciences	Cat# 340181
Experimental models: Cell lines
Human Embryonic Kidney (HEK) 293F	Dr Nicole Doria-Rose, VRC, USA	N/A
Recombinant DNA
HCoV-HKU1 and -OC43 spike plasmids	Dr Gaurav Kwatra and Prof Shabir A. Madhi, Wits VIDA, SA Prof Barney Graham, VRC, USA	N/A
Software and algorithms
FACSDiva 9	BD Biosciences	https://www.bdbiosciences.com
FlowJo 10	FlowJo, LLC	https://www.flowjo.com
Graphpad Prism 9	Graphpad	https://graphpad.com
BioRender	BioRender	https://biorender.com