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Doctors & Advice, Family Health

Virus Variants: What Can We Do To Stay Safe?

BY CARRIE MACMILLAN February 18, 2021

Yale experts discuss SARS-CoV-2 mutations, masks, humidity, and more.

For many of us, relief that vaccinations are being rolled out to protect us from COVID-19 is now tempered with anxiety about the intense media coverage of mutations to the virus (SARS-CoV-2) that causes it. 

Do these new variants allow it to spread more easily? Is the disease they cause more deadly? Should we take different safety precautions? Will the vaccinations be effective against them?

The answers to these questions are not fully known, but scientists are working hard to learn as much as possible, as fast as possible. We recently took some of the common questions we’re hearing to Yale Medicine physicians and public health experts. (Below are their answers.)

But the most important thing they want you to know is this: To stay safe and healthy, we must all remain vigilant in infection prevention during these critical next few months.

This, admits Richard Martinello, MD, a Yale Medicine infectious diseases specialist and Medical Director of Infection Prevention at Yale New Haven Health, is not always easy. 

“We have pandemic fatigue. We are enthusiastic about having vaccines, but we still need to adhere to all public health advice,” Dr. Martinello says. “We should continue taking all known protective measures. That includes wearing a mask, keeping physical distance, washing your hands often and well, and avoiding crowds and other groups of people whenever possible.” 

Why is the virus mutating? Is this bad news?

Mutations are a normal part of a viral life cycle, explains Akiko Iwasaki, PhD, a Yale immunobiologist and leading COVID-19 researcher. “Viruses mutate all the time, and that’s how they survive various environments,” she says. 

Not only that but mutation is actually key to how viruses spread, notes Nathan Grubaugh, PhD, a Yale School of Public Health epidemiologist. “Viruses mutate during each infection; what I’m worried about is ‘selection,’” he says. “Basically, selection is when mutations that help the virus survive get passed on to another host. Sometimes, selected mutations can help to make viruses more transmissible or evade immune responses.” Slowing transmission (through vaccination and other control measures) is key, he adds.

“Globally, we're playing a game of whack-a-mole—if we're trying to suppress transmission in one place to decrease variants, new ones will keep popping up,” says Grubaugh. “So, this really is a global problem and we all need to work together, especially on rolling out the vaccine, if we want to control new variants.”

If mutations are expected, why are we worried?

According to the Centers for Disease Control and Prevention (CDC), new variants sometimes disappear; other times, they persist and become dominant. Multiple variants of the virus that causes COVID-19 have been documented in the United States and around the world since the pandemic began. 

We have pandemic fatigue. We are enthusiastic about having vaccines, but we still need to adhere to all public health advice. Richard Martinello, MD, a Yale Medicine infectious diseases specialist

“This pandemic has gone on for over a year. It's caused millions of infections, which means there have  been so many different opportunities for selection to happen,” says Grubaugh. “As a result, some viruses now contain constellations of unique mutations, which are called variants.” 

Currently, three SARS-CoV-2 variants are causing concern—one first detected in the United Kingdom (known as B.1.1.7); one first detected in Brazil (P.1); and one first detected in South Africa (B.1.351). 

“Each seems to be more adept at spreading in a population of people. B.1.1.7 was originally identified last September and by December, it made up about 70% of all SARS-CoV-2 viruses,” Dr. Martinello says. “And when epidemiologists looked at the data, they found it seemed to spread at a rate of about 50 to 70% greater than other strains.” 

 As COVID-19 continues to spread, more variants are likely to appear. “We might be talking about three mutations, or we might be talking about 20 mutations that collectively change the behavior of the virus,” Grubaugh says. “They can make the viruses more transmissible, or they can make them more likely to evade our immune response, whether it’s naturally occurring or from a vaccine.”

How do we solve the problem of mutations?

If the virus spreads more easily, it means outbreaks that are already bad are made a little bit worse, Grubaugh adds. More infections lead to more hospitalizations, more strain on the health care system, and, thus, more deaths, experts say. 

That’s why it’s important to contain the viral spread as quickly and as effectively as possible, Iwasaki says. “That means everyone getting vaccinated, as well as maintaining the things that we've been doing—mask-wearing, hand-washing, and avoiding indoor crowds, to name a few,” she says. “But, because of the transmissibility of these new variants, we really need to double up on these efforts.”

Akiko Iwasaki, PhD (center), a Yale immunobiologist and leading COVID-19 researcher. “Viruses mutate all the time, and that’s how they survive various environments,” she says.


Grubaugh emphasizes that we, collectively, can make a difference in what happens. If, as individuals and as a community, we all do our part, the variants “won’t be able to take a foothold in our community,” he says. “If we don't act, within a couple of months one of these more transmissible variants might end up becoming the dominant virus in our community.” 

Will the vaccines protect against new variants?

Although new information is being released as doctors and researchers learn more, so far experts believe that the current vaccines will provide coverage—in some capacity—to the emergent variants. 

“[For the Pfizer-BioNTech and Moderna vaccines] it may not be the 95% protection that was shown in the initial clinical trials; instead it might be more like 90% or even 85% protection. We don't quite know yet, but we think it still is going to be a huge benefit,” Grubaugh says. He added that an updated vaccine may be needed in the future as more mutations occur.  

But, according to Heidi Zapata, MD, a Yale Medicine infectious diseases physician, early research indicates that the B.1.351 variant, first detected in South Africa, may present challenges. 

“It seems like the blood sera from vaccinated individuals with the Pfizer and Moderna vaccines can neutralize the B.1.1.7 variant. However, so far we’re seeing that sera from previously infected COVID patients isn’t able to fully neutralize the B.1.351 variant, which is concerning,” Dr. Zapata says. “When the sera of individuals vaccinated with Moderna and Pfizer vaccines was tested against the B.1.351 variant, a significant decrease was also noted in the neutralization of it—there was about a six-fold reduction in the effectiveness of the antibodies with the Moderna vaccine.”   

That being said, Dr. Zapata adds that these experiments only measure one type of immunity, which is formation of antibodies. “There are other parts of the immune response that we are not measuring, so we don’t totally know how this will play out in the real world,” she says. “We should remember that even if vaccines are not as effective against certain variants, they are offering some protection—this is still good and could help curb this pandemic.” 

Can doctors tell which variant a person with COVID-19 has?

No, unfortunately, says Dr. Martinello, who explains that standard COVID-19 tests in the U.S. do not include genetic sequencing, which is the only way to gather information about mutations. Only a small percentage of positive COVID tests are brought to laboratories for genetic sequencing, he says. 

“When the virus is sequenced, they compare it to other sequences of the virus from the past,” he explains. “They assign a genotype and can then measure what proportion of the virus [of the samples taken within a community] is this variant,” he says. Dr. Martinello adds that the United Kingdom, known for its outstanding public health program, sequences 10% of viruses, compared to about 0.3% here in the U.S. 

Surveillance, Grubaugh explains, is our “flashlight.” 

“Without it, we don’t know what is there. Across the country, public health programs are drastically ramping up their virus genomic surveillance programs to shed light on where these new variants are spreading,” he says. 

The [mutations] can make the viruses more transmissible, or they can make them more likely to evade our immune response. Nathan Grubaugh, PhD, a Yale School of Public Health epidemiologist

In Connecticut, the Yale Schools of Public Health and Medicine have formed a partnership with the Department of Public Health to increase variant surveillance. They obtain COVID-19 samples from throughout the state to screen for variants using simple molecular assays and confirm them via sequencing. This program found the first cases of the B.1.1.7 variants in Connecticut and is helping to track the spread of new introductions. (Click here for to see COVIDTrackerCT for more details.)

Should we still wear masks?

Mask-wearing remains key to containing the spread of any and all COVID variants, and the CDC recommends wearing one anytime you are indoors or outdoors with people who don’t live with you. Drs. Zapata and Martinello agree that, regardless of what people are reading about or seeing on television, the best mask to wear is one that fits well (snugly covering the nose and mouth without gaps on the sides) and meets established recommendations from the CDC.

The latest CDC guidance for improving mask use recommends wearing a cloth mask with multiple layers of fabric or one disposable mask underneath a cloth mask. It says a cloth mask can be combined with a fitter or a brace for better fit and extra protection. Currently, the CDC does not recommend the use of N95s for the general public because of supply issues. For people who wear KN95 masks, which meet similar requirements, the CDC warns that about 60% are counterfeit.

Is it safe to travel to visit friends and family?

Many people celebrated holidays without friends and family this year and are now itching to see loved ones, even if it means traveling. Acknowledging how hard this is, Dr. Martinello urges people to resist temptation and instead stay home, to the extent that it’s possible.

“We have consistently been told to minimize all nonessential travel, and it is really important that we continue to do that,” he says. “Otherwise we may find ourselves in a situation where these new variants dominate, and we may see higher rates of hospitalization.” 

However, that doesn’t mean you have to completely lock yourself in your home, Dr. Zapata says. 

“Honestly, online grocery shopping is more expensive than going yourself. I would argue that grocery shopping is essential and if you go, just be careful,” she says. 

We should remember that even if vaccines are not as effective against certain variants, they are offering some protection—this is still good and could help curb this pandemic. Heidi Zapata, MD, a Yale Medicine infectious diseases specialist

And if you do visit with others from outside your household inside, always wear a mask, Dr. Zapata adds. For essential workers whose jobs don’t allow them to stay home—including delivery drivers and retail employees—she offers the same advice of masking and washing hands often. One can also consider wearing eye protection depending on the kind of work done, she says. 

Should we monitor indoor humidity?

Another strategy to help prevent COVID-19 from spreading is to keep indoor relative humidity levels at 40 to 60%. There are several reasons why this is helpful, says Iwasaki.

“First, it reduces the viability of airborne viruses, including SARS-CoV-2. Second, it allows for the SARS-CoV-2 droplet to acquire water to ‘drop down,’ so it's no longer in the air. So, the ability or availability of the virus in the air is reduced at this relative humidity,” she explains. “And third, we’ve discovered this relative humidity level encourages the mucociliary clearance of the virus, so that even if you were to inhale viral particle, your ability to get rid of it, through coughing or swallowing, is enhanced at these humidity levels.” 

If you don’t already have a monitor that measures your indoor humidity in your home or office, you can buy a hygrometer. 

“If it is below 40%, I would recommend getting a humidifier,” says Iwasaki, cautioning against overdoing it, however. “If you were to keep it at 80 to 90% humidity, for example, you might actually promote the growth of molds. So, this sweet spot between the 40 to 60% is what I would recommend for every household, and hopefully, every public building can implement it as well.” 

In the end, Grubaugh says that we have all the tools needed to stop the spread of these new variants. “We know what works. We know that masks help reduce the risk of transmission. We know that social distancing reduces the risk of transmission,” he says. “We know that certain behaviors and especially being indoors with a lot of people with low ventilation can lead to transmission. And we know that vaccines will provide protection. It’s a matter of implementing these tools and actually using it to slow transmission.”