Condensed Statements of Operations and Comprehensive Loss (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Research and development expense to related party	$ 98	$ (217)	$ 315	$ 112

Research and development expense to related party.

No definition available.

Name:	pcvx_ResearchAndDevelopmentExpenseToRelatedParty
Namespace Prefix:	pcvx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration