CHARLOTTESVILLE, Va. — In terms of the COVID-19 vaccine, doctors are weighing in on the concept of delaying the second dose of the shot.

Dr. Bill Petri, an infectious diseases professor at the University of Virginia, has been studying the effects of COVID-19.

“We all need to be vaccinated so there's herd immunity that we can stop the pandemic,” Petri told WTKR.

He’s also keeping a close eye on the two-dose messenger RNA (mRNA) vaccines from Pfizer and Moderna.

“They're almost miraculous in their ability to protect us against COVID-19,” Petri said. “What we think the second dose is doing is to further develop the antibody response and help make it long-term.”

The CDC says the Pfizer doses should be administered three weeks apart, while Moderna's should be one month apart.

However, if the recommended interval isn't possible, the agency said the second dose may be administered up to six weeks, or 42 days, after the first dose.

“Under special circumstances, it's better to delay that couple of weeks than not do it at all,” Dr. Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases said.

Fauci said U.S. data from Moderna and Pfizer doesn't support the move of a second dose delay.

“We will go by the science, which is dictated for us, the optimal way to get the 94-95% response, which is in fact, durable for the period of time that we've been following it,” Fauci said.

Petri believes the second dose is crucial and that the shots work best within that three- or four-week time frame.

“The second dose is like the icing on the cake. That's what's going to give you the 95% and lock that in,” he said. “Moderna did their study with four weeks apart. Pfizer did it three weeks apart. We're kind of scared to vary from that because we know what works. It's kind of like, ‘Don't fix it if it's not broke.”

While there is wiggle room, Petri told WTKR that it's important to stay on schedule as best as possible for vaccination for the best protection, especially with new variants of the virus in the U.S.

“If we miss that second dose, your antibody levels are going to be a little bit lower,” Petri said. “The more that you can adhere to the schedule, the better the chances that your antibody levels are going to be high enough to protect you, even against these new variants of the coronavirus.”

This story was first reported by Zak Dahlheimer at WTKR in Norfolk, Virginia.