Elmira, NY (WENY)-- With both Pfizer and Moderna vaccines requiring second does, is it safe to cross vaccine doses?

While both vaccines use similar mechanisms to fight COVID-19, Arnot Health recommends getting both doses from the same brand.

"A lot of safety and exit data that we have for both of those vaccines, were done with each of those doses for the first and second doses," says Andrew Klee.

Klee works at Arnot Health as an infection prevention associate. He says the data that they have shows the vaccines work best when they are made by the same manufacturer. However, there are some circumstances in which a person could get a dose from a different manufacturer.

"There are limited circumstances," Klee said, "where for whatever reason you could not identify what the first dose was, or if there is a situation where the supply of those vaccines was not available anymore."

If you don't meet those circumstances, you should get the dose that you got the first time.

"We try to emphasize getting, for example, if you got the Pfizer dose, get the Pfizer dose for the second one, and likewise for the Moderna one," Klee explained.

While there is a grace period, people should get their second dose of the vaccine in the time line given to them.

"We would want to get as close as possible to whatever date that was for the second dose. There is a grace period," Klee said, "so we can administer that second dose four days prior, and we can delay it for upwards of six weeks past the first dose."

Klee says cards will be handed out that will have the type of vaccine and when to return for a second dose.