As expected, the first full winter of the Covid-19 pandemic in the United States has been brutal, bringing the total death toll approaching the half-million mark. There are also reasons to be hopeful: The daily average of new Covid cases is now declining in 43 states, and, while off to a shaky start, the rollout of Covid vaccines is underway. But this is SARS-CoV-2 we’re talking about, and the virus doesn’t care about fitting into any tidy little narrative where spring comes and everyone gets vaccinated, ultimately leading to the end of the pandemic and everyone frolicking maskless in a field.

Along with the positive news, there have also been reports confirming cases of infections and deaths caused by new variants of the virus that causes Covid-19. While it’s clearly not a step in the right direction, what exactly does that mean? Will the existing vaccines be effective against these new strains? And should we be doing anything differently to protect ourselves? Here’s what to know, along with a breakdown of some of the more prevalent variants so far.

It is normal for viruses to change

It is common for viruses to mutate over time, in some cases, forming new variants. “That is why we get a flu shot every year — because the flu virus changes and we have a new variant each year,” says Dr. Karin Michels, professor and chair of the Department of Epidemiology at the UCLA Fielding School of Public Health. “We may have to get the annual Covid shot from now on in addition to the annual flu shot.”

But not all variants have what it takes to stick around: some form and then disappear, while others persist and spread. While there is an ever-changing list of new SARS-CoV-2 variants, three have emerged that scientists are most concerned about — at least for now — in addition to the original virus.

The original virus 

On December 31st, 2019, health officials in Wuhan, China reported a cluster of pneumonia cases from an unknown cause, which they soon identified to be a novel coronavirus. Several weeks later, the International Committee on Taxonomy of Viruses (ICTV) announced that the new virus would be called “severe acute respiratory syndrome coronavirus 2” — or “SARS-CoV-2” for short — because while they are different, this virus is genetically related to the coronavirus responsible for the SARS outbreak of 2003. 

The same day, February 11th, 2020, the World Health Organization (WHO) revealed that the disease caused by SARS-CoV-2 would be known as “Covid-19.” As of February 19th, 2021, the WHO reports that there have been approximately 111 million cases of Covid-19, resulting in nearly 2.5 million deaths. 

The United Kingdom variant

Also known as variant B.1.1.7, this strain emerged from the U.K. in September 2020, and is now found in more than 80 countries. The first confirmed case in the United States came at the end of December, and as of February 21, 2021, a total of 1,661 cases have been reported across 42 states. 

Because it has been circulating for more than five months, scientists know more about this new strain than any of the others, but are still far from understanding its full impact. The most recent research from Public Health England estimates that the B.1.1.7 variant is between 30 to 50% more transmissible — meaning it spreads more efficiently and faster — than other strains. Other preliminary data out of the UK suggests that the strain comes with the possibility of more severe cases of Covid-19, and may be associated with a 30% increased risk of death compared with other variants — though, as BBC News points out, “the evidence is not strong and the data is still uncertain.” The CDC has predicted that B.1.1.7 will be the dominant strain in the United States by next month.

The South Africa variant

Although variant B.1.351 originated in South Africa close to the same time that the U.K. strain started spreading, the CDC says that it developed independently. It then became the dominant variant in Zambia in December 2020. Estimates from preliminary data indicate that this strain is 50 percent more transmissible than the previous strains that were circulating in South Africa. At this point, there is no evidence that B.1.351 causes a more severe form of Covid-19, according to the CDC. 

However, it is known that like the B.1.1.7 and P.1 variants, the B.1.351 variant contains a mutation in its spike protein that allows the virus to latch on to human cells more easily than the original iteration of SARS-CoV-2. The first infections caused by the B.1.351 strain in the United States were identified at the end of January 2021, and as of February 21st, a total of 22 cases have been reported across 10 states.

The Brazil variant

In early January 2021, a new strain of the virus known as P.1 was first identified in travelers from Brazil during routine Covid testing at an airport in Japan. By the end of the month, it had been detected in the United States, and as of February 21st, a total of five cases have been reported across four states. 

There is currently no microbiological or epidemiological evidence of increased transmissibility of P.1 — but the presence of a mutation also found in the UK and South Africa variants indicates that it is plausible — nor is there any evidence of an increase in the severity of the resulting infections. Additionally, according to the CDC, this variant contains a set of additional mutations that may affect its ability to be recognized by antibodies — meaning that if a person was infected with the original virus, the antibodies they developed may not protect them against this variant. 

What does this mean for the Covid-19 vaccines that have already been developed?

After all the drama and excitement of the race for a vaccine, finding out about these new variants making their way around the world — just as the vaccine rollout is getting started — might feel a little soul-crushing. But that’s not the right way to look at it, says Dr. Sten Vermund, an infectious disease epidemiologist and professor at the Yale School of Public Health.

Take, for example, recent clinical trial data from Novavax, which indicated that their Covid vaccine candidate is around 85 percent effective against the U.K. variant, and approximately 50 percent effective against the South Africa strain. But, as Vermund puts it, an efficacy rate of “50 percent is huge,” because that means there’s the possibility that there will be enough cross-reacting antibodies to at least blunt the severity of the infection in all recipients. “So the people who get infected and get sick are not going to get as sick, because having immunity to a mismatched variant is better than having no immunity at all,” he explains.

So far, both Pfizer-BioNTech and Moderna have reported that their vaccines are effective against the B.1.1.7 (UK) variant, but didn’t fare as well against the B.1.351 variant (first detected in South Africa). The vaccines’ efficacy against the P.1 variant out of Brazil is not yet known. Currently, both Pfizer and Moderna are working on booster shots which, if necessary, could offer increased protection to those who have received the original formulation of the vaccine.

For now, Vermund says that we should continue to get the currently available vaccines, as planned. “The quicker we suppress transmission globally, the fewer variants will emerge, and the more efficacy our current vaccines will have in real-world use,” he explains. 

How can we protect ourselves against the new variants?

According to Vermund, we should be taking the same steps and precautions that have been recommended throughout the pandemic — except with everyone actually making an effort this time. “Folks haven’t been necessarily rigorous in applying the classic public health strategies,” he says. “For example, one sees a lot of mask use which is not correct. Lots of people have their mask below their nose. Lots of people don’t have well-fitting masks.”

Additionally, both Vermund and Michels stress the importance of keeping as much space as possible — but at least 6 feet — between yourself and other people. “A lot of people are very relaxed with their six-foot distancing,” Vermund explains. “And, you know, that was not arbitrary. We came up with the six feet from real-world data. People have to respect that.”

So how worried should we be about the new variants? “Very worried,” Michels says. “But even more worried about new mutants that may circumvent the currently-available vaccines — because the virus aims to evade our immune response. Indeed, the new variants are more aggressive and may make you sicker than the original strain, so I would be — and am — even more cautious.”