Nature of Business (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) segment	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Aug. 13, 2021 USD ($)	Dec. 31, 2019 USD ($)
Nature of business:
Operating segments | segment			2
Accumulated deficit	$ (197,473,680)		$ (197,473,680)		$ (193,214,134)
Net loss	(1,897,068)	$ (2,776,763)	(4,259,546)	$ (10,358,097)
Net cash used in operating activities			(5,644,147)	(4,338,530)
Cash and cash equivalents	28,979,969	$ 11,168,305	28,979,969	$ 11,168,305	18,676,663		$ 5,420,708
Cash and cash equivalents, period increase (decrease)			10,303,306
Period increase (decrease) as a percent			55
Working capital	25,228,135		$ 25,228,135		13,386,485
Working capital increase, decrease					11,841,650
Working capital increase (decrease) as a percent			88.00%
Grants Receivable, Current	117,680		$ 117,680		203,774
Debt instrument, face amount	10,000,000.0		$ 10,000,000.0		$ 20,000,000.0
FBR Sales Agreement
Nature of business:
Borrowing capacity						$ 2,000,000.0
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:
Term (in years)			two years
NIH
Nature of business:
Grants Receivable, Current	$ 1,800,000		$ 1,800,000
Collaborative arrangment, transaction with party | CiVax
Nature of business:
Revenue from collaborative arrangement			1,500,000
Collaborative arrangment, transaction with party | NIAID | Government contract
Nature of business:
Revenue from collaborative arrangement			$ 700,000
Term (in years)			five years
Collaborative arrangment, transaction with party | DTRA | Government contract
Nature of business:
Revenue from collaborative arrangement			$ 600,000
Term (in years)			three years