Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Financial Instruments Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Assets:
Investments, Fair Value	$ 123,188
Fair Value, Recurring
Assets:
Cash and cash equivalents, Amortized Cost	238,185	$ 68,986
Cash and cash equivalents, Gross Unrealized Losses	(12)	(1)
Cash and cash equivalents, Fair Value	238,173	68,985
Investments, Amortized Cost	124,080	204,342
Investments, Gross Unrealized Losses	(892)	(240)
Investments, Fair Value	123,188	204,102
Total assets measured at fair value, Amortized Cost	362,265	273,328
Total assets measured at fair value, Gross Unrealized Losses	(904)	(241)
Total assets measured at fair value, Fair Value	361,361	273,087
Fair Value, Recurring \| Cash \| Level 1
Assets:
Cash and cash equivalents, Amortized Cost	164,147	27,834
Cash and cash equivalents, Fair Value	164,147	27,834
Fair Value, Recurring \| Money Market Funds \| Level 1
Assets:
Cash and cash equivalents, Amortized Cost	20,107	17,555
Cash and cash equivalents, Fair Value	20,107	17,555
Fair Value, Recurring \| U.S. Treasury Securities \| Level 1
Assets:
Cash and cash equivalents, Amortized Cost	0
Cash and cash equivalents, Fair Value	0
Investments, Amortized Cost	45,090	45,290
Investments, Gross Unrealized Losses	(278)	(73)
Investments, Fair Value	44,812	45,217
Fair Value, Recurring \| Commercial Paper \| Level 2
Assets:
Cash and cash equivalents, Amortized Cost	47,441	23,597
Cash and cash equivalents, Gross Unrealized Losses	(11)	(1)
Cash and cash equivalents, Fair Value	47,430	23,596
Investments, Amortized Cost	31,874	61,941
Investments, Gross Unrealized Losses	(43)	(22)
Investments, Fair Value	31,831	61,919
Fair Value, Recurring \| U.S. Government Agency Securities \| Level 2
Assets:
Cash and cash equivalents, Amortized Cost	6,490
Cash and cash equivalents, Gross Unrealized Losses	(1)
Cash and cash equivalents, Fair Value	6,489
Investments, Amortized Cost	15,653	24,714
Investments, Gross Unrealized Losses	(220)	(46)
Investments, Fair Value	15,433	24,668
Fair Value, Recurring \| Corporate Debt \| Level 2
Assets:
Investments, Amortized Cost	21,183	58,498
Investments, Gross Unrealized Losses	(317)	(74)
Investments, Fair Value	20,866	58,424
Fair Value, Recurring \| Asset-backed Securities \| Level 2
Assets:
Investments, Amortized Cost	10,280	13,899
Investments, Gross Unrealized Losses	(34)	(25)
Investments, Fair Value	$ 10,246	$ 13,874

Cash and cash equivalents amortized cost.

No definition available.

Name:	pcvx_CashAndCashEquivalentsAmortizedCost
Namespace Prefix:	pcvx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Cash and cash equivalents and investments.

+ References

No definition available.

+ Details

Name:	pcvx_CashAndCashEquivalentsAndInvestments
Namespace Prefix:	pcvx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Cash and cash equivalents and investments amortized cost basis.

+ References

No definition available.

+ Details

Name:	pcvx_CashAndCashEquivalentsAndInvestmentsAmortizedCostBasis
Namespace Prefix:	pcvx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Cash and cash equivalents and investments gross unrealized loss before tax.

+ References

No definition available.

+ Details

Name:	pcvx_CashAndCashEquivalentsAndInvestmentsGrossUnrealizedLossBeforeTax
Namespace Prefix:	pcvx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Cash and cash equivalents gross unrealized loss before tax.

+ References

No definition available.

+ Details

Name:	pcvx_CashAndCashEquivalentsGrossUnrealizedLossBeforeTax
Namespace Prefix:	pcvx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_AssetsFairValueDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124260329&loc=d3e26610-111562

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

No definition available.

+ Details

Name:	us-gaap_CashAndCashEquivalentsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_CashMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_MoneyMarketFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: