WATCH: Fauci says vaccine hesitancy will lead to ‘two Americas’

CNN's Don Lemon lamented that the US will "fall short" of President Biden's goal of having the nation vaccinated to 70 percent by July 4. Concerns about vaccination rates lead to worries that there will be big outbreaks in locations where people are hesitant to get the shot.

He told Lemon on Tuesday that "When you have such a low level of vaccination superimposed upon a variant that has a high degree of efficiency of spread, what you are going to see among under vaccinated regions—be that states, cities or counties—you're going to see these individual types of blips."

"It's almost like it's going to be two Americas," Fauci said. "You're going to have areas where the vaccine rate is high, where it's more than 70 percent of the population that have received one dose. When you compare that with areas where they have 35 percent of the people vaccinated, you clearly have a high risk of seeing these spikes in selected areas," Fauci said.

"This is entirely avoidable, entirely preventable. If you are vaccinated, you diminish dramatically your risk of getting infected, and even more dramatically, your risk of getting seriously ill. If you are not vaccinated, you are at considerable risk," he said.

Fauci also said that there's basically no point in getting an antibody test to see if you have antibodies that would fight the virus. Instead, he assumes, according to Insider, that he will need a booster shot at some point, after the protections from the vaccine have faded.

"You don't want to assume that you're going to have indefinite durability of protection," he said, and it won't be the antibody test that lets him know when a new dose of vaccine is needed.

"If I went to LabCorp or one of those places and said, 'I would like to get the level of anti-spike antibodies,' I could tell what my level is, if I wanted to," he said. "I didn't do it."

He's looking out for breakthrough infections in those who participated in early vaccine trials, and lab data showing the waning of vaccine efficacy. That's when he'll know that he needs to get a booster, he said.

Antibody tests, according to the FDA, are all about detecting natural infection and antibodies, not immunity protections. In fact, antibody tests that test for natural antibodies and those that test for vaccine-earned antibodies don't even test for the same viral protein.

However, Fauci said that the antibody tests will still be used to see how well the vaccines are performing over a long term. The number of people who participated in the vaccine trials were "literally tens of thousands of people," Fauci said.

Fauci's prediction is that people will continue to need booster shots, and that this could basically be determined on population level, based on given risk factors, like age and overall health. "You don't have to all individually get a blood test," Fauci said.