Vaccinated and confused? Answers about masks, Delta variant and breakthrough infections

Although the COVID vaccines are highly effective, no vaccine offers 100% protection. While breakthrough infections happen, they are rare, and in most cases, breakthrough infections cause only mild illness.


The World Health Organization wants everybody to wear masks, but the U.S. Centers for Disease Control and Prevention says vaccinated people often don’t need to wear them.

So whom do we listen to?
Virus experts and public health researchers also offer mixed advice, but largely agree on one point: Whether a fully vaccinated person needs to wear a mask really depends on the circumstances and what is happening in that person's community.

“At this point, thinking about wearing a mask is a little like dressing for the weather,” said Linsey Marr, a professor of civil and environmental engineering at Virginia Tech and one of the world’s leading experts on viral transmission. “You need to consider the caseload and vaccination rates wherever you’re going, what activity you’ll be doing, and your own health.”

But the new push to ask vaccinated people to mask up has sown confusion. Does the call for masking mean the vaccines don’t offer enough protection? Why is everyone so concerned about the delta variant? And should vaccinated people be worried about breakthrough infections? Here are some answers.

Why is the WHO telling vaccinated people to wear masks?
Mask mandates are largely intended to protect the unvaccinated — people who are vaccinated are already well protected by vaccines, and breakthrough infections are still very rare. But since you can’t always tell who is vaccinated and who is not, telling everyone to wear a mask can help stop the spread of the virus by people who are infected but don’t have any symptoms.

And while cases and deaths are falling in the United States, large parts of the world are still grappling with high case counts, and many people remain unvaccinated.

“WHO is providing guidance for the whole world, and in areas where delta is dominant, cases are high, vaccination rates are low, and the vaccines that have been distributed are less effective against delta, it makes sense for vaccinated people to wear masks,” Marr said.

CDC Director Dr. Rochelle P. Walensky stood by advice that people fully vaccinated against the coronavirus do not need to wear masks in most situations, but added that there were instances where local authorities might impose more stringent measures to protect the unvaccinated.

Marr said her advice to a fully vaccinated friend about mask wearing would be to follow local mask rules and to take extra precautions in certain situations.

“I would tell them that, in general, they do not need to wear a mask,” Marr said. “But they should continue to carry one with them for times when they are in a very crowded indoor setting for a long period of time, like air travel, where masks are required anyway, or a crowded movie theater, playhouse or concert venue, for example.”

If I’m vaccinated, should I be worried about the delta variant?
The delta variant, which was first identified in India, is worrisome because it is highly contagious and spreading rapidly around the globe. Unvaccinated people who are infected with delta are twice as likely to be hospitalized as those infected with alpha, the variant first detected in Britain.

What has been surprising about the delta variant is how easily it seems to be transmitted. In Australia, security cameras documented a brief encounter of two people passing each other in a shopping mall; one of them was unknowingly infected. The shoppers were facing each other at one point and breathed each other’s air for only seconds, which led to the second person getting infected. (The transmission was confirmed through genetic sequencing.) While such a brief encounter typically wouldn’t lead to transmission, the case signals how important it is that people get vaccinated before the delta variant spreads further.

The delta variant now accounts for more than half of all infections in the United States, according to estimates from the CDC.

But if you are among the vaccinated, most experts say you don’t need to be fearful. All of the vaccines in use in the United States offer significant protection against delta. Studies in Britain, Scotland and Canada show that two doses of the Pfizer vaccine offer from 79% to 88% protection against the delta variant, compared with 93% protection against alpha.

A study from Israel found that the effectiveness of the Pfizer-BioNTech vaccine was 64%. Moderna has said test tube studies using blood samples from vaccinated people shows the vaccine is still highly effective against the delta variant, which caused only a “modest reduction” in virus-fighting antibodies in the samples. And Johnson & Johnson released two studies that showed its vaccine remained effective against delta, showing only a small drop in potency.

Gregg Gonsalves, assistant professor of epidemiology at the Yale School of Public Health, said that vaccinated people should feel confident they were protected, but that he would continue to mask in grocery stores and other public spaces.

“There are enough people unvaccinated that we should be modeling good behavior, showing social solidarity,” he said.

What’s my risk of getting COVID-19 after I’m fully vaccinated?
Although the COVID vaccines are highly effective, no vaccine offers 100% protection. While breakthrough infections happen, they are rare, and in most cases, breakthrough infections cause only mild illness.

The risk of being hospitalized or dying as a result of a breakthrough infection is minuscule (less than 0.0006%), based on data collected from the CDC. As of July 6, more than 157 million people in the United States had been fully vaccinated against COVID-19. As of that date, the CDC reported 5,186 patients with COVID-19 vaccine breakthrough infections that resulted in hospitalization or death, including 4,909 who had been hospitalized and 988 who had died.

But because the risk of getting COVID-19 after vaccination isn’t zero, some health experts still advise that vaccinated people take reasonable precautions, like wearing a mask in crowded spaces. People who live in areas with low vaccination rates may also want to consider wearing masks in public, where they are more likely to encounter an unvaccinated person than someone living in a highly vaccinated region.

In the United States, 64.7% of people 12 and older have received at least one dose and 55.9% are fully vaccinated. But the pace of vaccinations varies. Several states in the South, including Mississippi, Tennessee, Alabama and Arkansas, have vaccinated fewer than 50% of adults.

Dr. Paul Offit, a professor at the University of Pennsylvania and a member of the Food and Drug Administration’s vaccine advisory panel, is fully vaccinated but wears a mask on public transit and in the grocery store.

Offit said the risk rose in a community where most people weren't vaccinated, because it created more opportunities to encounter the virus. He cites a study in the Netherlands of the measles vaccine, which, like the COVID vaccine, offers high levels of protection, that found an unvaccinated person was safer in a highly vaccinated community than a vaccinated person in an area with low vaccination rates.

“If you’re in a highly vaccinated community you have sort of a moat around you,” he said.

Offit said the problem with the current guidance about mask wearing in the United States is that it requires trust.

“You have to trust that the other people you’re coming into contact with are vaccinated if they’re not wearing a mask,” Offit said. “That’s a lot to trust. The same people who aren’t masked often aren’t vaccinated. Those two things usually go hand in hand. When you see people masked inside, they’re often the ones who are vaccinated.”

Marr added that everyone should be prepared for evolving guidance on masks, distancing and other precautions.

“I know everyone wants this to be over or wants a one-size-fits-all rule," Marr said. "But we need to get used to things changing as the virus changes, vaccines roll out, public health responses in different countries shift, and scientists learn more. The 1918 flu pandemic lasted two years.”


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