Table 1.

Here we review these four major classes and discuss their similarity and distinctiveness as vaccine adjuvants.

Category		Laser type	Wavelength	Target Spot Size	Pulse Duration	Pulse Frequency	Pulse Energy	Average Power	Exposure Duration	Putative Mechanisms of action	Tested in	References
Conterminal	Ultra-short pulsed (UPLVAs)	Copper vapor	511/578 nm	5–10 mm in diameter	10–25 ns	5 – 20 kHz	60 μJ	1 – 6 W/cm2	1–3 min	Extracellular release of HSP70 to enhance APC activation and antigen presentation	Mice, humans	[22,23]
		Q switched Nd:YAG	532 nm	7 mm in diameter	6–7 ns	10 Hz	30 mJ	0.78 W/cm2	1–4 min	Derangement of connective tissue facilitates migration of APCs	Mice	[21,24,25]
		Q switched Nd:YVO4	532 or 1064 nm	5 mm in diameter	7 ns	10 kHz	67 μJ	1 – 5 W/cm2	1–4 min	Photochemical, photothermal and photoacoustic stimulation of tissue leading to APCs activation and migration	Mice	[26]
		modelocked Ti:Al2O3	780 nm	0.5 μm	200 fs	76 MHz	n.d.	n.d.	2 min	Membrane permeabilization effects	Mice	[31]
	Nonpulsed (NPLVAs)	CW Nd:YVO4	1064 nm	5 mm in diameter	N/A	N/A	N/A	5 W/cm2	1–4 min	Photochemical reaction in skin tissue leading to immunostimulatory microenvironment for APCs	Mice	[26]
Fractional	Nonablative (NAFLVAs)	Fractional ER:Glass	1410 nm	7 x 10 mm	10 ms	15.4 Hz	15 mJ	n.d.	1–2 sec	Sterile inflammation caused by an array of MTZs in skin recruit and activate DCs	Mice, pigs	[33,34]
	Ablative (AFLVAs)	Fractional ER:YAG	2940 nm	14 mm2	75 μs	200 Hz	n.d.	n.d.	Several seconds	The mild inflammatory milieu created in the dermis by skin laser microporation itself activates APCs	Mice	[37]

Nd:YVO4: Neodymium-Doped Yttrium Orthovanadate; Nd:YAG: Neodymium-Doped Yttrium Aluminum Garnet; ER:YAG: Erbium:Yttrium-Aluminium-Garnet; CW: Continuous Wave; MTZ: Microthermal Zone; APC: Antigen Presenting Cell; DC: Dendritic Cell; n.d: Not Described.