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VERIFY: How necessary is that second COVID-19 shot?

Last week, the CDC published a report showing 80% effectiveness in preventing COVID-19 infections after a single mRNA shot. Does that mean you can skip the second?

CHARLOTTE, N.C. — State data shows full vaccinations rising in the Carolinas. According to North Carolina's Department of Health and Human Services, nearly 2 million people have gotten both of their Pfizer or Moderna shots, meaning about 20% of the state population has completed the vaccine process.

In South Carolina, the Department of Health and Environmental Control reports almost 800,000 people, or 19% of the Palmetto State, are finished with their vaccinations.

That said, not everyone is returning for that second shot. In fact, DHEC recently reported an uptick in people skipping that next appointment.

But with new data showing high protection from a single mRNA shot, is a second one necessary?

THE QUESTION

Is the second dose of an mRNA vaccine, like Pfizer's or Moderna's, still needed?

THE ANSWER

Yes, despite some protection produced after a first dose, the Centers for Disease Control and Prevention and health experts say a second dose is needed to be considered fully vaccinated and some immunity benefits could be lost by skipping that second shot.

"To me, it's like a law enforcement officer wearing a bullet-proof vest on only one half of their chest," Nick Davidson, South Carolina's Senior Deputy for Public Health, said.

According to the CDC report, researchers looked at nearly 4,000 frontline workers in eight U.S. cities over 13 weeks. They found a single dose of Pfizer or Moderna had 80% effectiveness after 14 days. However, 14 days after a second dose, the effectiveness in preventing coronavirus infection rose to 90%.

"I think that's a positive story to tell people," Dr. Lewis McCurdy, infectious disease specialist at Atrium Health, said. "After the first one, you're getting some protection. I think what we've shown is that maximal protection is after that second dose."

McCurdy said people ready to settle for the lesser effectiveness should consider another factor too.

"After the first dose, you get some protection, but what we don't know, and this is why I would encourage people to follow what the science is suggesting, that second dose may really prolong your duration of immunity," McCurdy said. "So, you're really protected for a longer period of time."

In fact, one of the conclusions drawn in that CDC report was further support for the current vaccine schedule.

"They reinforce CDC's recommendation of full 2-dose immunization with mRNA vaccines," the report said.

Have a relative or friend in another state and want to know when they can get vaccinated? Visit NBC News' Plan Your Vaccine site to find out about each state's vaccine rollout plan.