Annual report pursuant to Section 13 and 15(d)

Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation - Additional Information (Details)

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Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation - Additional Information (Details) - USD ($)
1 Months Ended 12 Months Ended
Sep. 25, 2018
Aug. 31, 2019
Sep. 30, 2018
Feb. 28, 2017
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Aug. 04, 2021
Jan. 01, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Reserved common stock         11,221,420 8,331,103      
Aggregate intrinsic value of stock options exercised         $ 2,800,000 $ 1,200,000 $ 200,000    
Expected dividend         0.00%        
Weighted-average estimated grant-date fair value of employee stock options granted         $ 14.24 $ 5.59 $ 6.71    
Share-based compensation arrangement by share-based payment award options, shares granted         266,724 266,724      
Stock-based compensation expense         $ 23,241,000 $ 11,917,000 $ 10,312,000    
Liability attributable to call option plan         $ 97,000 $ 109,000      
Restricted Stock Units                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Shares vesting period         4 years        
2018 Equity Incentive Plan                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Reserved common stock 2,300,000                
Annual increase period of common stock reserved for issuance 10 years                
Maximum number of shares issuable                 2,287,605
2018 Equity Incentive Plan | Employee Stock Options                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Total unrecognized compensation cost related to unvested granted         $ 24,700,000        
Remaining unrecognized compensation cost expected to be recognized over weighted-average period         2 years 6 months        
2018 Equity Incentive Plan | Restricted Stock Units                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Total unrecognized compensation cost related to unvested granted         $ 36,300,000        
Remaining unrecognized compensation cost expected to be recognized over weighted-average period         3 years 2 months 12 days        
2018 Equity Incentive Plan | Employee Stock Purchase Plan                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Unrecognized stock-based compensation expense         $ 100,000        
2018 Equity Incentive Plan | Maximum                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Increase in stock reserved for issuance as percentage of capital stock outstanding on last day of preceding year 5.00%                
2018 Employee Stock Purchase Plan                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Reserved common stock     230,000            
Annual increase period of common stock reserved for issuance     10 years            
Maximum number of shares issuable     2,300,000   145,809 195,992 131,939    
Shares available for grant         673,251        
Shares available for grant, increase                 457,521
2018 Employee Stock Purchase Plan | Maximum                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Increase in stock reserved for issuance as percentage of capital stock outstanding on last day of preceding year     1.00%            
Call Option Plan                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Stock-based compensation expense         $ 97,000 $ 109,000 $ 78,000    
Other income (expense)         $ 109,000 $ (76,000) $ (153,000)    
Call Option Plan | Option Granted in February 2017                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Share-based compensation arrangement by share-based payment award options, shares granted       248,944          
Call options expiration period       1 year          
Call Option Plan | Option Granted in August 2019                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Share-based compensation arrangement by share-based payment award options, shares granted   17,780              
Call options expiration period   1 year              
Call Option Plan | January 1 , 2017 | Option Granted in February 2017                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Call options vesting percentage       25.00%          
Call Option Plan | January 1 , 2018 | Option Granted in February 2017                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Call options vesting percentage       25.00%          
Call Option Plan | January 1 , 2019 | Option Granted in February 2017                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Call options vesting percentage       25.00%          
Call Option Plan | January 1 , 2019 | Option Granted in August 2019                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Call options vesting percentage   25.00%              
Call Option Plan | January 1 , 2020 | Option Granted in February 2017                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Call options vesting percentage       25.00%          
Call Option Plan | January 1 , 2020 | Option Granted in August 2019                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Call options vesting percentage   25.00%              
Call Option Plan | January 1 , 2021 | Option Granted in August 2019                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Call options vesting percentage   25.00%              
Call Option Plan | January 1 , 2022 | Option Granted in August 2019                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Call options vesting percentage   25.00%              
Call Option Plan | Vaxcyte, Inc.                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Reserved common stock         266,724        
2021 Equity Inducement Plan                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Reserved common stock               750,000  
2018 Equity Incentive Plan and 2021 Equity Inducement Plan                  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                  
Shares available for grant         1,504,641