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Fully vaccinated people experiencing breakthrough COVID infections: What to know

The highly contagious delta variant is continuing to spread across the US, causing more fully vaccinated to become infected. But experts say that's not a reason to question vaccines.

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Even though they can contract the delta variant, vaccinated people are far less likely to end up in the hospital.

Sarah Tew/CNET
For the most up-to-date news and information about the coronavirus pandemic, visit the WHO and CDC websites.

The highly contagious delta variant is continuing to spread across the US, causing a spike in COVID-19 infections -- especially in areas with low vaccination rates. What's different about this variant? It's also breaking through to infect fully vaccinated people. Studies by the US Centers for Disease Control and Prevention say the delta infection has similarly high viral loads in vaccinated and unvaccinated people. So what does that mean as more of these breakthrough cases continue happening? 

Currently, 167 million people in the US have been fully vaccinated, a little over half the country's total population. The CDC's research suggesting that vaccinated people infected with delta can also easily transmit the virus was the key factor motivating the new federal guidance that fully vaccinated individuals continue to wear masks indoors. At the same time, the CDC report underlines that the number of cases and deaths among fully vaccinated people is small compared with the unvaccinated. 

Should you be concerned about getting COVID-19 if you've already been inoculated? Since there's more community spread and there are more breakthrough cases despite vaccination, new data suggests yes. We'll explain what a breakthrough coronavirus infection is, how it's possible for fully vaccinated people to become infected and what it all means. This information comes from the CDC, the World Health Organization and other experts.

What a breakthrough COVID-19 infection means

A breakthrough COVID-19 infection is when a fully vaccinated person becomes infected with the coronavirus without any symptoms or experiences symptoms, is hospitalized or dies from the infection. A small percentage of fully vaccinated people can get COVID-19 if exposed to the virus, but they're much less likely to become sick, according to the CDC

If someone's fully vaccinated and does test positive for coronavirus, it's likely they'll have milder symptoms (see below) or be asymptomatic as Dr. Clare Rock, a Johns Hopkins medical professor, told me. 

Now that it's been determined fully vaccinated people can be infected with high viral amounts of the delta variant, the CDC is concerned they can transmit the virus. If you do become ill, experts urge you to isolate yourself to prevent others from getting sick, especially people with medical vulnerabilities.

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How can fully vaccinated people become infected with coronavirus?

Someone can become infected with COVID-19 just before or right after they get the vaccination, because it takes roughly two weeks before the vaccine is most effective. However, even after the immunity builds up, there's still a chance they can become infected, according to the WHO, since the vaccines aren't silver bullets against disease (though they're highly effective).

With millions of unvaccinated people around the world, new variants will emerge, Rock says. For example, the delta variant can pose a threat to people who are fully vaccinated -- especially those who have high-risk medical conditions (see the next section).

Dr. Anthony Fauci said that more COVID-19 testing needs to be done on fully vaccinated people to better understand the breakthrough cases.

Can coronavirus symptoms still be severe if you're fully vaccinated?

Someone who's fully vaccinated has a much smaller risk of experiencing severe symptoms from COVID-19. People who've received all their doses of a vaccine are less likely to be hospitalized or die than those who haven't been vaccinated, the CDC says. Vaccinated people typically see symptoms like a runny nose, which they mistake for a sign of a common cold, Rock said.

But that's not to say serious cases can't happen. The CDC says some fully vaccinated people can still be hospitalized and die. This can include people who have medical conditions that make them immunocompromised, Rock said, including those with cancer and people who've had organ transplants -- in general, people who are more vulnerable. Data released in Israel by the Israeli Health Ministry shows that people who are unvaccinated are five times more likely to experience a severe infection, as opposed to the elderly who are fully vaccinated, Haaretz reported.

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It's possible for a fully vaccinated person to become infected with COVID-19.

Sarah Tew/CNET

How can you keep yourself protected from breakthrough COVID-19 infections?

If you're fully vaccinated but worried about getting sick, you can take the following precautions. 

  • Wear a mask in public places.
  • Practice social distancing.
  • Keep your home well-ventilated by opening windows.
  • Wash your hands.
  • Get a COVID-19 test if you're experiencing symptoms.

Will fully vaccinated people eventually have to get booster shots?

Given the current circumstances, it's likely a booster shot will be necessary. The Food and Drug Administration is expected to authorize a COVID-19 booster shot by the weekend, but the CDC will need to also give authorization before booster shots can be distributed. The shot would be a third dose of the Pfizer and Moderna vaccines.

Scientists are continuing to study the immunity of fully vaccinated people to get a better idea of how well the vaccines protect them. Moderna is currently researching when a booster shot may be necessary. For instance, Rock said vulnerable people who don't have a robust immune system -- such as those with chronic medical conditions -- may need an additional shot.

Pfizer says it's working on a booster shot for its COVID-19 vaccine (PDF) to enhance immunity among those who've already received both doses. The UK is also prepping for booster shots, with vaccine experts in the UK saying a booster shot may be needed before winter.

Which variants are causing the COVID-19 breakthrough infections?

The variant causing the most concern right now is the delta variant, which is now the dominant strain in the US and other countries. This variant has caused an increase in COVID-19 cases, which is also affecting people who are fully vaccinated. 

In comparison with the alpha variant, researchers have found delta to be 60% more transmissible, and hospitalization risks are much higher in unvaccinated people.

In most instances, the cases are happening in areas with low vaccination rates. For instance, US states like Louisiana and Florida have low vaccination rates and their COVID-19 cases are surging again.

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Wearing a mask can help you protect yourself from COVID-19.

Sarah Tew/CNET

What experts saying about the efficacy of vaccines against coronavirus

The breakthrough infections don't mean the vaccines aren't powerful.

"The effectiveness against severe disease is still substantial," Fauci said during a White House press briefing July 22. "Get vaccinated. It offers good protection against disease."

The main reason for breakthrough cases is the number of people who still haven't been vaccinated. Once more people are fully vaccinated, the virus likely won't infect as many people. Until then, the virus can continue to mutate and spread, creating new variants.

For more information, here's everything to know about the delta variant. Also, here are more details about a potential COVID-19 booster shot, and info on the debate over whether fully vaccinated people should wear masks.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.