(CNN) A subvariant of Omicron, BA.2, is leading to a new wave of Covid-19 infections across Europe. Cases in the United Kingdom, Germany, the Netherlands and other countries are going up, driven by this very contagious coronavirus strain.
The proportion of Covid-19 cases due to BA.2 is rising in the United States, too. The US Centers for Disease Control and Prevention now estimates that 35% of new coronavirus cases are due to this subvariant. At the same time, restrictions are being lifted, and not a single US state requires mask mandates anymore (though masks are still required in some settings, including airports, public transportation, hospitals, nursing homes, and some schools and workplaces).
How worried should people be about the BA.2 variant? Will vaccines protect against it? What if someone contracted a previous variant -- could they become reinfected? Is BA.2 milder than previous versions, and if so, should people try to get it? Could BA.2 cause another surge in the US, and is it time for restrictions to be put back into place?
To help us with these questions, I spoke with CNN Medical Analyst Dr. Leana Wen, an emergency physician and professor of health policy and management at the George Washington University Milken Institute School of Public Health. She is also author of "Lifelines: A Doctor's Journey in the Fight for Public Health."
CNN: What do we know about BA.2, and how worried should we be about it?
Dr. Leana Wen: With any new variant or subvariant, we need to ask three questions: Is it more contagious? Does it cause more severe disease? And does it evade the protection of our vaccines?
BA.2 is related to BA.1, which is the original Omicron subvariant that led to the huge surge in cases over the winter here in the United States and across Europe. BA.1 swept through communities because of how contagious it is. BA.2 appears to be even more contagious than BA.1. The UK Health Security Agency estimates that BA.2 is growing 80% faster than BA.1. Here in the US as well, BA.2 appears to be on its way to overtaking BA.1 to become the dominant variant.
The good news is that BA.2 does not seem to cause more severe illness than BA.1. Researchers from the UK and Denmark have found BA.2 causes a level of hospitalization that's comparable to that of BA.1, which is less likely to result in severe illness than the previously dominant Delta variant.
In addition, the vaccines we have are still effective. While vaccination may not protect as well against infection with BA.1 and BA.2, the effectiveness in that regard is partially restored with a booster dose, and the vaccines continue to provide very good protection against severe illness due to both Omicron subvariants.
What all of this says to me is that public health experts should follow the rise of BA.2 in the US closely, but that most people should not be worried. It's likely that the US will see an increase in Covid-19 cases in the coming weeks, as this is the pattern we've seen before -- that we lag behind the UK and Europe by a few weeks, so the increase they are seeing could be mirrored here. However, most people who are vaccinated, and in particular if they are boosted, are unlikely to become severely ill due to BA.2. Our government officials should prepare for what could be coming and increase the availability of tests and treatments, and continue to urge people to get vaccines and boosters. But I don't think this is something that the general public should be overly concerned about at this time.
CNN: Does that mean people can proceed with spring break and other travel plans, or do they need to postpone them?
Wen: I don't think travel plans need to be put on hold. To be sure, there is uncertainty, as some places might have low rates of Covid-19 now but may have increased rates when you travel. However, that may be the case for the foreseeable future. Very few activities that we do have no risk. Traveling certainly entails risk, but you can reduce that risk by making sure you are vaccinated and boosted. Wearing a mask in crowded indoor settings further reduces risk. In the United States, follow the CDC guidance and make sure to wear a mask in areas that have high Covid-19 community levels. If you are planning international travel, know the rules, including whether you have to have proof of vaccination or a recent negative test.
CNN: Are there certain people who should be concerned about BA.2?
Wen: Individuals who are very vulnerable to severe illness from Covid-19 despite vaccination should be concerned about the coronavirus in general, as they are about other infectious pathogens. For most people, Covid-19 infection will result in mild illness, but in some people --those who are moderately or severely immunocompromised or with multiple underlying medical conditions -- the infection still could result in hospitalization. BA.2 may not cause more severe disease than BA.1, but because of how contagious it is, people who are particularly vulnerable will want to keep taking additional precautions. That includes wearing a high-quality mask (N95, KN95 or KF94) in all indoor public settings, avoiding large crowds and traveling for essential reasons only. Before getting together with other people, they may wish to request that the others are tested for Covid-19.
CNN: If someone previously had Omicron, are they protected against BA.2?
Wen: The World Health Organization has said that infection with BA.1 continues to provide protection against BA.2. Reinfection with BA.2 after having BA.1 is rare.
Most people don't find out what variant they had, though this could be estimated based on when they got infected. If someone found out that they had Covid-19 during the initial Omicron surge, it's likely they had BA.1. In that case, especially if they are vaccinated too, they are very unlikely to contract BA.2.
However, if someone was previously infected during another wave, for example, while Delta was predominant, they could still contract BA.1 or BA.2. This is another reason why vaccination is so crucial, because the combination of vaccination and prior infection provides more consistent and more durable protection than prior infection alone.
CNN: Omicron is a milder variant than previous variants. In that case, should people try to contract BA.2 just to get it over with?
Wen: In general, it is not a good strategy to try to contract an illness. Omicron is less likely to result in severe disease compared with Delta, but it still causes severe illness in some people. In addition, even mild illness may be very unpleasant and result in feeling unwell, missing work and being unable to care for family members for days. You could also infect other people, and there is the possibility of long-haul symptoms as well. A better strategy is to make sure to get the vaccine and booster so that if you were to encounter BA.2 (or another variant of Covid-19), you are as well protected as possible.
CNN: Could BA.2 cause another surge in the US, and if so, should restrictions come back now?
Wen: BA.2 could certainly lead to another uptick in Covid-19 infections in the US. There are already some signs that the sharp decline in new cases is leveling out, and if the US follows Europe, as it has before, a rise in cases could be weeks away.
That said, I don't think it means we need to reinstate restrictions. The goal of vaccination is to decouple infections from hospitalizations and severe illness. If there is a surge in infections but hospitalizations don't rise to the point that our health care system becomes overwhelmed, then I think government-imposed mandates are not warranted. Here, the new CDC guidelines are very helpful, as they take into account severe illness -- severe enough to cause hospitalizations -- as the metric for masking, not just any infection.
Of course, just because the government isn't requiring masks doesn't mean that individuals shouldn't mask or take other precautions. At this point in the pandemic, people should make decisions based on their own medical circumstances and tolerance of risk.