What happens if you only get the first COVID vaccine and not the second dose?


This question was answered live at the virtual conference titled, "Don’t Hesitate to Vaccinate! Our Experts Tell You Why" recorded on January 28, 2021.

Short Answer: 

For the Moderna and Pfizer vaccines, the first dose is designed to train your body to recognize the virus and ramp up the immune system. The second shot strengthens that response.

With what we are using currently Pfizer's vaccine is 52% effective after the first shot, and 95% effective after the second dose. Moderna's vaccine is also just over 50% effective after the first shot, and 94.5% effective after the second dose.

The newest Johnson & Johnson COVID vaccine only requires one dose of the vaccine.


It takes time for your body to build protection after any vaccination. COVID vaccines that require 2 shots may not protect you until a week or two after your second shot. You can wait up to three weeks from the first dose to get the second dose. Recently the CDC has come out that you can go out as far as three weeks between the COVID vaccine doses because some people are traveling for work, or another unique circumstance.

Learn More >>

We know at least one future potential vaccine will require only a single dose, but we are waiting for the FDA to approve this vaccine.

Presenters include:

Dr. Jamal Gwathney, Clinical Director, Metropolitan Correctional Center, San Diego Federal Bureau of Prisons; National Public Health Officer
Dr. Rodney Hood, President and Chairman, Multicultural Health Foundation, and Tri-Chair, COVID-19 Vaccine Advisory Committee
Dr. Wilma Wooten, Public Health Officer and Director of Public Health Services, County of San Diego, Health and Human Services Agency

Click here for the latest COVID-19 information in the County of San Diego >>

* Funded by the County of San Diego in support of the Live Well San Diego vision.

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Together Against COVID is an initiative led by the Multicultural Health Foundation (MHF) in partnership with the County of San Diego. MHF's mission is to bring health justice and wellness to the multicultural communities of San Diego County by focusing resources on the most vulnerable populations with community-based wellness strategies, social-clinical interventions, and research that will lead to the elimination of racial and ethnic health disparities. For more information, please contact us at (619) 915-6734.