Equity Incentive Plans - Summary of Activity Under Stock Option Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Number of Options
Options granted (in shares)			29,638
Weighted- Average Exercise Price Per Share
Weighted-average exercise price per share, options exercised (in dollars per share)	$ 9.09	$ 13.79	$ 13.00	$ 10.16
2020 Plan and 2014 Plan \| Employee Stock Option
Number of Options
Beginning balance (in shares)			9,366,936
Options granted (in shares)			1,701,746
Options exercised (in shares)			(549,602)
Options forfeited (in shares)			(54,066)
Ending balance (in shares)	10,465,014		10,465,014		9,366,936
Vested and expected options (in shares)	10,465,014		10,465,014
Options exercisable (in shares)	5,621,921		5,621,921
Weighted- Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Beginning Balance (in dollars per share)			$ 39.40
Weighted-Average Exercise Price Per Share, Options granted (in dollars per share)			62.24
Weighted-average exercise price per share, options exercised (in dollars per share)			13.00
Weighted-Average Exercise Price Per Share, Options forfeited (in dollars per share)			67.30
Weighted-Average Exercise Price Per Share, Ending Balance (in dollars per share)	$ 44.36		44.36		$ 39.40
Weighted-Average Exercise Price Per Share, Vested and expected to vest (in dollars per share)	44.36		44.36
Weighted-Average Exercise Price Per Share, Exercisable (in dollars per share)	$ 31.71		$ 31.71
Weighted-Average Remaining Contractual Term (Years) and Aggregate Instrinsic Value
Weighted-Average Remaining Contractual Term (Years)			7 years 5 months 4 days		7 years 5 months 23 days
Weighted-Average Remaining Contractual Term (Years), Vested and expected to vest			7 years 5 months 4 days
Weighted-Average Remaining Contractual Term (Years), Exercisable			6 years 5 months 26 days
Aggregate Intrinsic Value	$ 54,196		$ 54,196		$ 406,730
Aggregate Intrinsic Value, Vested and expected to vest	54,196		54,196
Aggregate Intrinsic Value, Exercisable	$ 48,942		$ 48,942
2020 Plan and 2014 Plan \| Performance Contingent Stock Options (PCSOs)
Number of Options
Beginning balance (in shares)			639,710
Options forfeited (in shares)			(17,850)
Ending balance (in shares)	621,860		621,860		639,710
Vested and expected options (in shares)	621,860		621,860
Options exercisable (in shares)	0		0
Weighted- Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Beginning Balance (in dollars per share)			$ 102.70
Weighted-Average Exercise Price Per Share, Options forfeited (in dollars per share)			102.70
Weighted-Average Exercise Price Per Share, Ending Balance (in dollars per share)	$ 102.70		102.70		$ 102.70
Weighted-Average Exercise Price Per Share, Vested and expected to vest (in dollars per share)	$ 102.70		$ 102.70
Weighted-Average Remaining Contractual Term (Years) and Aggregate Instrinsic Value
Weighted-Average Remaining Contractual Term (Years)			9 years 4 months 6 days		9 years 10 months 6 days
Weighted-Average Remaining Contractual Term (Years), Vested and expected to vest			9 years 4 months 6 days
Aggregate Intrinsic Value	$ 0		$ 0		$ 0
Aggregate Intrinsic Value, Vested and expected to vest	0		0
Aggregate Intrinsic Value, Exercisable	$ 0		$ 0

Vaxcyte, Inc. 10-Q