More than 120 million Americans have joined what is arguably the most sought-after club in the world: those who are immunized against the coronavirus. Fully vaccinated people were given the go-ahead by the Centers for Disease Control and Prevention in March to meet with other fully vaccinated or unvaccinated low-risk people from another household without a mask and travel without quarantine earlier this month . (As reports of state and local case variability increase, the CDC increasingly urges caution.)
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But what about all of the people – a number that is impossible to count despite being estimated at millions – who now have some level of immunity from having recovered from Covid-19?
The agency recommends that everyone – vaccinated, rescued, or otherwise – wear a mask in public.
There is no mention of whether people who have recovered can gather without covering their faces like those who are fully vaccinated.
And the need for masks remains a controversial issue. As the federal government doubles its importance, some states have exercised caution – and turned to the wind. We decided to explore the science and motivations behind the masking recommendation.
I beat Covid! Ain’t that behind me
People who recover from the virus enjoy some immunity. According to the CDC, protection will last at least 90 days after testing positive for the virus. During this time, they do not need to be quarantined or retested if they are re-exposed.
Reinfection cases are rare. While those infected can shed the virus for months after they recover, the amount is so small, according to the CDC, that it is unlikely to infect others.
In light of this, some have questioned whether people who have recovered still need to comply with mask mandates. Linsey Marr, an engineering professor at Virginia Tech University who studies airborne transmission, told us that people who have had the virus don’t have strong scientific reasons for covering their faces.
However, key questions about the level of post-infection immunity that make it advisable to continue wearing a mask remain open, experts say. For example, scientists have yet to determine whether people who experienced mild or no symptoms evoked a sufficient immune response to meaningfully protect them from getting the virus again.
Also, nobody knows how long the immunity will last. A person could become re-infected and spread the virus without knowing it, said A. Oveta Fuller, associate professor of microbiology and immunology at the University of Michigan Medical School.
“You don’t want to bring viruses into the environment,” she said.
What Makes Vaccines More Protective?
The Covid vaccines available in the USA offer a high level of protection against illness, hospitalization and death.
The Moderna and Pfizer-BioNTech vaccines are over 94% effective after two doses. The percentage for the Johnson & Johnson vaccine is lower – 72% in the US. These vaccines cannot be accurately compared for various reasons. (On Tuesday, the FDA recommended a break in the use of the J&J vaccine as reports of rare side effects are investigated.)
So far, studies suggest that Moderna and Pfizer-BioNTech injections will protect people for at least six months, but the research is still ongoing. These dates are not yet available for the J&J inclusion.
Scientific evidence also seems to show that immunity induced by vaccines is stronger than what the body produces after infection, Fuller said. And vaccines seem to offer some protection against the variant discovered in the UK, which is now widely used in the US. Whether natural immunity can fight this strain or other variants is unknown, said CDC spokesman Jade Fulce.
What could be responsible for these differences? Visualize the virus as a hand, Fuller said. Natural infection causes the body to attack every part of the pathogen, including expendable parts like the tip of a fingernail. However, the vaccines were designed to develop fighters who respond to the virus’ thumb, the spike protein that binds it to the human cell.
“We know the thumb is critical to infection,” said Fuller.
New evidence suggests that the vaccines could also prevent or limit how much the virus replicates in the airways, which could further reduce transmission.
The immunity induced by vaccines, however, is associated with a proportion of unknowns. Vaccines have a high rate of effectiveness, but they still don’t protect 100% from the virus. Scientists are still figuring out whether immunity to vaccines or infection will wane over time.
Depending on how that protection dissipates, people with vaccine-induced immunity could become susceptible to the virus again and become infected without knowing it, Fuller said. Infected people can shed the virus up to two days before symptoms appear, and an estimated 30% never show signs of illness.
“We learned a lot,” Fuller said in the year since Covid appeared. “But there is so much more to know.”
A mask protects you, your neighbor and the world
When a person infected with SARS-COV-2 exhales, they release droplets into the air that contain moisture, saliva, and possibly bits of virus.
Masks prevent these droplets from landing in or on another person. Tightly woven fabrics can trap smaller droplets than those made with loosely woven fabrics, said Richard Sachleben, a retired chemist. Some versions also help the wearer breathe fewer viruses.
Droplets of different sizes are associated with different risks, said Sachleben. Big ones are pulled to the ground by gravity, he said, but they’re more dangerous because they carry more viruses than smaller ones that linger in the air. Fortunately, they are also easier to block with a face covering.
“That’s why a shitty mask is better than no mask,” said Sachleben.
Face covering also helps prevent more variants from forming, because the fewer particles there are in the air, the less chance the virus has of mutating into a form that is more resistant to human defenses.
However, not even the best masks are 100% effective at catching and blocking every virus, said Dr. Donald Milton, professor of environmental health in the University of Maryland School of Public Health. However, when combined with other public health measures, they can significantly reduce the spread of viruses.
“If you combine a mask that works a little on me with a mask that works a little on you when you’re outside or well ventilated inside,” he said, “these things add up.”
Wearing a mask also sends a message about what people need to do to “break the back of this pandemic,” Fuller said. Since face coverings protect the public from the wearer’s germs, it is also communicated that the wearer cares about the community, Sachleben said.
“If you wear a mask, it means that you care,” Sachleben said. “If I wear a mask, it means I’ll take care of you.”
KHN (Kaiser Health News) is a national newsroom that produces extensive journalism on health issues. Alongside Policy Analysis and Polling, KHN is one of the three most important operational programs of the KFF (Kaiser Family Foundation). KFF is a foundation that provides health information to the nation.
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