Since COVID-19 vaccines started rolling out, experts have been discussing the process of herd immunity, also called herd protection.

But what exactly does that mean?

"If you're able to reduce the amount of susceptible individuals in a community, you can interfere with its spread even to other susceptible members,” explained Dr. Pedro Piedra, a professor of molecular virology and microbiology at Baylor College of Medicine.

The way a vaccine generally works is the more people are vaccinated, the harder it is for the virus to spread. The flu vaccine, for example, needs about 80 percent coverage to reduce transmission for herd immunity. If eight out of ten people are vaccinated, the virus eventually dies down before getting to the two who either can’t for medical reasons, or just choose not to get the shot. If only half are protected, the virus has a better chance at staying alive and continuing the cycle.

Piedra says COVID-19 vaccines will likely need a similar percentage of the population vaccinated.

“Viruses that spread very efficiently, you need higher vaccine coverage,” Piedra said. “And SARS-cov-2 has spread very efficiently."

Research so far shows COVID-19 vaccines work a little differently. For example, both the Moderna and Pfizer vaccines need two doses to work efficiently.

“We've seen several people between their first and second dose get exposed or have a positive test,” said Department of State Health Services Regional Medical Director Emilie Prot. “They are taking more risky behaviors because of that first dose."

Prot said studies show after a second dose, there’s a 95 percent effectiveness against hospitalization.

Even if eight out of ten people have been vaccinated, those two people could still see the worst outcome possible from COVID-19, which is why medical professionals are recommending to get vaccinated if you can.

For now, doctors are reminding people the best defense is the three Ws: Wash your hands, wear a mask and watch your distance.