Quarterly report pursuant to Section 13 or 15(d)

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

v3.20.2
Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation - Additional Information (Details) - USD ($)
1 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended
Sep. 26, 2018
Sep. 25, 2018
Aug. 31, 2019
Feb. 28, 2017
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Dec. 31, 2019
Jan. 01, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Reserved common stock         8,691,304   8,691,304   7,357,234  
Aggregate intrinsic value of stock options exercised         $ 5,000 $ 9,000 $ 81,000 $ 55,000    
Weighted-average estimated grant-date fair value of employee stock options granted         $ 5.60 $ 6.79 $ 5.03 $ 6.97    
Share-based compensation arrangement by share-based payment award options, shares granted             266,740   266,640  
Stock-based compensation expense         $ 3,011,000 $ 2,463,000 $ 5,718,000 $ 4,749,000    
Liability attributable to call option plan         $ 2,100,000   $ 2,100,000   $ 76,000  
Restricted Stock Units                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Restricted common stock granted             497,250      
Shares vesting period             4 years      
Shares vesting date             2024-05      
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                   1,154,948
Shares available for grant         1,970,938   1,970,938      
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         $ 6,200,000 1,500,000 $ 6,200,000 $ 1,500,000    
Remaining unrecognized compensation cost expected to be recognized over weighted-average period             2 years 9 months 18 days 2 years 4 months 24 days    
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         20,100,000 21,400,000 $ 20,100,000 $ 21,400,000    
Remaining unrecognized compensation cost expected to be recognized over weighted-average period             2 years 7 months 6 days 3 years 1 month 6 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 0 $ 100,000 $ 0    
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       483,066   483,066      
Shares available for grant         206,404   206,404      
Shares available for grant, increase                   230,989
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         $ 64,000 17,000 $ 68,000 35,000    
Other expense net         $ 1,800,000 $ 3,000 $ 2,000,000.0 $ 7,000    
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       248,960     248,960      
Call options expiration period       1 year            
Share-based compensation arrangement by share based payment award options, exercise price per share             $ 1.28      
Call Option Plan | Option Granted in February 2017 | January 1 , 2017                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Call options vesting percentage       25.00%            
Call Option Plan | Option Granted in February 2017 | January 1 , 2018                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Call options vesting percentage       25.00%            
Call Option Plan | Option Granted in February 2017 | January 1 , 2019                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Call options vesting percentage       25.00%            
Call Option Plan | Option Granted in February 2017 | January 1 , 2020                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Call options vesting percentage       25.00%            
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       17,780      
Call options expiration period     1 year              
Share-based compensation arrangement by share based payment award options, exercise price per share             $ 2.04      
Call Option Plan | Option Granted in August 2019 | January 1 , 2019                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Call options vesting percentage     25.00%              
Call Option Plan | Option Granted in August 2019 | January 1 , 2020                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Call options vesting percentage     25.00%              
Call Option Plan | Option Granted in August 2019 | January 1 , 2021                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Call options vesting percentage     25.00%              
Call Option Plan | Option Granted in August 2019 | January 1 , 2022                    
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         266,740   266,740