Nature of Business (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($)	Aug. 13, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Nature of business:
Operating segments | segment			2
Accumulated deficit	$ (201,061,231)		$ (201,061,231)			$ (193,214,134)
Net loss	(3,587,551)	$ (1,790,160)	(7,847,097)	$ (12,148,257)
Net cash used in operating activities			(8,684,266)	(7,329,471)
Cash and cash equivalents	28,867,487	$ 11,342,794	28,867,487	$ 11,342,794		18,676,663	$ 5,420,708
Cash and cash equivalents, period increase (decrease)			10,190,824
Period increase (decrease) as a percent			55
Working capital	24,648,908		24,648,908			13,386,485
Working capital increase, decrease			$ 11,262,423
Working capital increase (decrease) as a percent			84.00%
Grants Receivable, Current	44,184		$ 44,184			$ 203,774
FBR Sales Agreement
Nature of business:
Borrowing capacity					$ 26,800,000
Late withdrawal loan
Nature of business:
Maximum borrowing capacity					5,000,000
Line of credit
Nature of business:
Debt instrument, face amount					5,000,000
Loan and security agreement
Nature of business:
Debt instrument, face amount					$ 10,000,000.0
CiVax
Nature of business:
Revenue from collaborative arrangement			$ 1,500,000
Term (in years)			two years
NIH
Nature of business:
Grants Receivable, Current	$ 1,600,000		$ 1,600,000
NIAID | Government contract
Nature of business:
Revenue from collaborative arrangement			$ 700,000
Term (in years)			five years
DTRA | Government contract
Nature of business:
Revenue from collaborative arrangement			$ 600,000
Term (in years)			three years