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  • About 5,800 fully vaccinated Americans have been recorded with Covid-19 so far, according to the US Centres for Disease Control.
  • Such "breakthrough" cases are to be expected, the CDC said, as vaccines aren't 100% effective.
  • Breakthrough infections are rare, affecting around 0.009% of vaccinated individuals, but they're more common in older adults.
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More than one in five Americans has been fully vaccinated against Covid-19. But vaccinated people can still get the coronavirus, though infections are exceedingly rare and typically quite mild, official numbers from that country shows.

Of the 66 million people across the US who were fully vaccinated as of April 13, some 5,800 still tested positive for Covid-19 - what's known as a "breakthrough infection" - according to new data available from the Centers for Disease Control and Prevention.

A few of those infections in vaccinated individuals were severe. Around 400 of the 5,800 people with breakthrough infections required hospitalization, and 74 died from the disease, the CDC said in a statement.

The report is another reminder that, as the US scientific lead on the the coronavirus Anthony Fauci and other public health experts have been stressing for months now, vaccination is not a one and done silver bullet to end the pandemic. Mask-wearing and social distancing still remain critically important, until we have enough immunity to eliminate the virus from circulation.

'The vaccine is working as expected'

These so-called "breakthrough" infections are to be expected, according to the CDC, and are in line with how other vaccines work.

"We expect thousands of vaccine breakthrough cases will occur even though the vaccine is working as expected," the statement said.

"With the number of breakthrough cases, I think the important thing is to look at what the denominator of vaccinated people is," Fauci, the top infectious-disease expert in the US, said during a White House press briefing last week.

Breakthrough infections have occurred in about 0.009% of the people who've had their Covid-19 shot(s), and then allowed them two full weeks to take effect. They have been so rare that the Minnesota Health Department tallied zero deaths in the first 89 breakthrough infection cases in that state.

"It's important to know that even if someone is vaccinated and then goes on to be one of the few unfortunate people to develop a breakthrough case, there still can be some level of protection provided by the vaccine," Minnesota infectious disease director Kris Ehresmann said during a March briefing on the subject.

The breakthrough rate of infections in Minnesota at that time was around 0.01%.

The new figures released from the CDC also suggest that authorized COVID-19 vaccines are near perfect at preventing death, as clinical trials had suggested. With 74 fatalities and 66 million people fully vaccinated, the vaccines appear 99.999% effective at eliminating death.

Some people who are vaccinated and subsequently get infected may not even know it, either, as about a third of the breakthrough infections (29%) were asymptomatic (only discoverable with a test).

Older adults who've been fully vaccinated are more likely to get infected

CRISTINA QUICLER / Contributor / Getty Images

The risk of breakthrough infection is not equally divided among everyone who's been vaccinated. The CDC said about 40% of the breakthrough infections reported so far have been discovered in people over the age of 60, where vaccines are often less effective.

"It is likely that elderly individuals, particularly if they are frail and have underlying conditions, might not have responded as well to the vaccine," Fauci said. "When someone is already elderly and may or may not have an underlying condition, that it is unfortunate, but not surprising that you might have a couple of deaths."

A nationwide "vaccine breakthrough database" has been created for American state health departments to help the US federal government monitor ongoing cases.

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