Second dose of COVID-19 vaccine, possible with residual vaccine

A friend said that he is looking for a second dose of the corona vaccine as a residual vaccine. Three weeks after the first dose, you can receive the remaining vaccine from today.

The second inoculation is automatically booked after the first inoculation.



Janssen needs 1 hit and Pfizer and Modder get 2 hits to gain immunity.

US Centers for Disease Control and PreventionEbony Johnson & Johnson's Janssen is said to be immune to one dose, while Pfizer and Moderna need two doses.


  • Johnson & Johnson Janssen (J&J/Jansens) COVID-19 vaccine provides complete immunity with a single dose.
  • Pfizer Biontech's COVID-19 Vaccine and Moderna's COVID-19 Vaccine require two doses to maximize immunity. You should get a second dose even if you experience side effects after your first dose, unless your vaccine provider or your doctor tells you not to get the dose.



The interval between the 1st and 2nd vaccinations is 3-4 weeks.


US Centers for Disease Control and PreventionAccording to the report, the second dose is 2 weeks after the first dose for Pfizer and 1 weeks for Moderna.


vaccine Vaccination age Number of vaccinations required
When are you considered to be fully vaccinated?
Pfizer 12 years old or older 2 times (3 weeks apart)
2 weeks after the second inoculation
moderna 18 years old or older 2 times (4 weeks apart)
2 weeks after the second inoculation
Janssen 18 years old or older 1rd time
2 weeks after inoculation



Due to the good supply of vaccines, the date of the second vaccination was delayed.

Based on the above criteria, the second vaccination should be given 1-3 weeks after the first vaccination. However, the second vaccination was scheduled after 4 weeks due to poor supply. This time, the supply of vaccines has improved, so it has been extended from 2 weeks to 6 to 2 weeks.


Comparison of 2nd vaccination reservation base date and residual vaccine 2nd vaccination interval (source)




From September 9, the second dose of the vaccine can be received as a residual vaccine.

Korea Policy BriefingAccording to the report, reservations for the remaining vaccine were only possible for the first dose, but from September 1, the second dose can also be reserved.



How to schedule a second dose of vaccine

I thought that the remaining vaccine reservations could only be made through Naver or the Kakao App, but after looking at the data, you can call a medical institution and put it on the list of vaccination reservations.

From the 17th, the second inoculation using the ΔSNS same-day quick reservation service (reservation of residual vaccines through Naver and Kakao apps) and Δpreparatory list for each medical institution (the method of individually contacting medical institutions and uploading them to the inoculation reservation list) is possible.


That's why my friend called the hospital and said that he was put on the waiting list.



If you make a reservation for the remaining vaccine, the previous reservation for the second vaccination will be automatically canceled.

The system seems to be well prepared. It is convenient because you do not have to cancel by calling the place where you received the first vaccination.


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