Breaking News
More () »

VERIFY: Is there a difference between COVID-19 vaccine dose one and two?

Both Pfizer and Moderna's COVID-19 vaccines require two shots to reach the maximum level of protection against the virus. Are the two doses different?

ROCK HILL, S.C. — State health agencies collectively report tens of thousands of people in the Carolinas are now considered "fully vaccinated," meaning they have received two doses of either the Pfizer or the Moderna vaccine.

The companies report both their vaccines are roughly 95% effective in preventing the virus, but a person needs two shots to get that level of protection.


Is there a difference between dose one and dose two of the currently approved COVID-19 vaccines?


The first dose and second dose of your Pfizer or Moderna COVID-19 vaccine should be exactly the same, both chemically and from a dosage standpoint. 

According to the manufacturer's instructions for the two approved vaccines, Pfizer and Moderna, doses must be spaced apart. 

For Pfizer, it's three weeks between doses. For Moderna, it's one month.

However, each manufacturer only provides one set of instructions, with no difference in directions between dose one and dose two.

Moderna's instructions read: "The Moderna COVID-19 Vaccine is administered intramuscularly as a series of two doses (0.5 mL each) 1 month apart."

Pfizer's instructions read: "The Pfizer-BioNTech COVID-19 Vaccine is administered intramuscularly as a series of two doses (0.3 mL each) 3 weeks apart."

Dr. Brannon Traxler, Interim Public Health Director with South Carolina's Department of Health and Environmental Control, confirms there is no difference between the two doses.

"They are exactly the same, in terms of the chemical makeup, but what they do and their function is a little bit different," Traxler said.

RELATED: WHO: 'Not right' to vaccinate young before old

Traxler states the function of dose one is that of a primer. 

"It gets (the immune system) ready and gets it started -- so, making antibodies and producing that immune response," Traxler said. "Then, the second dose --which again, in the syringe is identical -- but it is a booster. It boosts your immune system's response to more significantly produce antibodies."