ATLANTA (NewsNation Now) — As more Americans get vaccinated against the coronavirus, many are questioning how long will that protection will last.

Pfizer and Moderna have warned that it’s likely the world will need yearly booster shots, although some scientists question if such shots are necessary.

Infectious disease expert Dr. Anthony Fauci and leaders of major pharmaceutical companies support the idea.

So far, the vaccines have proven to be good at keeping people from getting sick, even if they do become infected.

However, there’s speculation that due to the various variants of the virus an annual shot may be needed, similar to what’s seen with the flu shot.

Meanwhile, some scientists are warning it’s important to consider the business goals of the vaccine developers when considering a booster, too. They say right now there’s no evidence that the COVID-19 vaccine protection against the deadly virus is fading.

“I really would like to know what they’re basing that evidence on, based on the science I’ve seen so far,” said Dr. Cecli Bennett with Newnam Family Medicine.

“It’s a little bit preliminary because we are, right now, in the middle of this trial … the data that I see coming there supporting the notion that likely there will be a need for a booster somewhere between eight and 12 months,” said Pizer CEO Albert Bourla. “But that remains to be seen, and I believe in one, two months we will have enough data to speak about it with much higher scientific certainty.”

There’s still a lot of unknowns to sort out if more shots are needed. It’s unclear if the booster would be an identical shot or a modified one, and then there’s figuring out a time frame for how soon people would need another dose.