Surgeon General warns unvaccinated people 'you're in trouble' as Delta variant spreads in the US

• Vaccination makes a big difference against the Delta variant, the US Surgeon General said Wednesday
• "If you are not vaccinated, then you're in trouble," Dr. Vivek Murthy told CNN.
• The Delta variant is becoming dominant in the US, but vaccines are still effective.

Vaccination confers a "high degree of protection" against the Delta variant, US Surgeon General Dr. Vivek Murthy said on Wednesday.

However, those who skipped getting fully vaccinated "are in trouble," he told CNN's Erica Hill.

As of Tuesday, the Delta variant made up 26,5% of new COVID-19 cases in the US, according to the CDC.

Some analyses suggest that it may already be the dominant variant in the US, after surging to prominence only a few months after it was discovered in India.

"The good news is that if you're vaccinated, and fully vaccinated - that means two weeks after your last shot - then there is good evidence that you have a high degree of protection against this virus," Murthy said.

Although no vaccine is 100% effective, the chances of fully vaccinated people getting sick or transmitting the virus "are low," he said.

"But if you are not vaccinated then you are in trouble," he said, adding: "This is a serious threat and we're seeing it spread among unvaccinated people."

Murthy's remarks are in line with findings from the UK, where the variant makes up more than 95% of cases.

British data shows that two doses of a vaccine are highly protective against developing even mild symptoms after catching the Delta variant: 88% for the Pfizer vaccine, and 60% for the AstraZeneca vaccine.

One dose of either is less protective against developing mild symptoms of the disease: 33% in both types.

However, a single dose of either vaccine offers substantial protection against developing a worse version of COVID-19. The AstraZeneca shot offers 71% efficacy against hospitalization, while the Pfizer shot offers 94% protection, data from the UK shows.

Laboratory experiments also suggest that the Moderna vaccine remains effective against the Delta variant, although real-world data has not been published.

No data has been published about Johnson & Johnson vaccine efficacy against the Delta variant. But in another interview with CNBC's "The News with Shepard Smith" on Wednesday, Murthy said that there are "reasons to be hopeful" that it remains protective.

"The J&J vaccine has proven to be quite effective against preventing hospitalizations and deaths with all the variants that we've seen to date," he said.