Collaboration Agreement - Additional Information (Detail) $ in Millions		6 Months Ended
	Jul. 20, 2020 USD ($)	Jun. 30, 2021 USD ($) Disease	Jun. 30, 2020 USD ($)	Mar. 31, 2021 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized as a cumulative catch-up adjustment		$ 20.5
Sanofi Collaboration And License Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maximum number of infectious disease pathogens for vaccine development		10
Sanofi Collaboration And License Agreement [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of infectious disease pathogens for vaccine development | Disease		7
Sanofi Collaboration And License Agreement [Member] | Minimum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of infectious disease pathogens for vaccine development | Disease		3
Second Sanofi Amendment Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional Upfront Payment	$ 300.0
Original Sanofi Agreement And Second Sanofi Amendment Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Increase in transaction price		$ 108.7
Non-refundable upfront payment		345.0
Amended Sanofi Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments achieved		50.0		$ 25.0
Collaboration receivable milestone payments achieved		4.0
Sanofi Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Remaining performance obligation, expected to be recognized as revenue		$ 597.0
Number of infectious disease pathogens for vaccine development | Disease		5
Upfront payment received		$ 45.0
Technology and process transfer milestone payment receivable		10.0
Estimated reimbursable employee cost		76.3
Estimated reimbursable development cost		167.8
Estimated milestone payments		212.0
Revenue recognized from contract liabilities		$ 29.8	$ 6.4
Sanofi Agreement [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of infectious disease pathogens for vaccine development | Disease		6
Sublicense Second Amendment Agreement With Sanofi [Member] | Massachusetts Institute Of Technology Exclusive Patent License Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional Upfront Payment Receivable		$ 75.0
Milestone payment receivable upon the achievement of additional specified regulatory development manufacturing and commercial milestones		1,900.0
Lumpsum or one time manufacturing milestone amount receivable		200.0
Maximum development and regulatory milestone payment receivable		148.0
Sars Cov2 Licensed Filed [Member] | Sublicense Second Amendment Agreement With Sanofi [Member] | Massachusetts Institute Of Technology Exclusive Patent License Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maximum development and regulatory milestone payment receivable		250.0
Additional Paid-in Capital [Member] | Securities Purchase Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Shares issued during the period value		$ 51.2