Why the Covid-19 BA2 variant may not cause a large wave of cases in the United States

A sub-variant of the coronavirus omicron BA.2 has been on the country’s radar for several months – scientists monitoring sewage noticed it back in January. BA.2 first attracted widespread attention in early February as it seemed to have caused a big wave of infections in the UK. And since then, some health experts have warned that this new iteration of the virus – which is spreading even faster than the super-contagious original version of the omicron – could create another wave in the pandemic.

So where is that wave? The number of cases at the national and even at the state level does not show growth. In the last two weeks in the United States, the number of new cases reported every day has been equal. Hospitalizations and deaths still falling from their peaks during the omicron wave. In some states, there has been an increase in cases – particularly in New York and Massachusetts – but there are still few signs of serious jumps. For example, in Nevada, where new cases have increased by 73 percent in the past two weeks, the actual number of infections is still quite low: 171 cases a day. Apart from the last few weeks, the number of cases has not been so low since May 2020.

None of the half-dozen experts I spoke to wanted to be too precise about what was happening. There is still a possibility that in some places the cases will increase. For example, it’s too early to know whether that 73 percent increase in daily cases in Nevada is a highlight or the beginning of exponential growth. But at this point most of them think the BA.2 wave could be rather rippled.

This has happened before. Some alarming options appeared and disappeared in the U.S. without causing a nationwide wave: after the alpha option was discovered in late 2020, health officials feared a new surge, but it didn’t happen. (The devastating winter wave of that year was mostly caused by the original virus.)

“The situation is very reminiscent of last year’s alpha wave, which many feared would cause a big spring wave here in the U.S., but it was only registered as a sign of our decline from the winter wave,” said Spencer Fox, deputy director. from the Covid-19 Model Consortium of the University of Texas.

Other experts have similar expectations. “I don’t believe BA.2 will be associated with an explosion similar to what we saw earlier in January,” said Wafaa al-Sadr, an epidemiologist at Columbia University.

Justin Lesler, who helped drive the Covid-19 modeling effort at the University of North Carolina, told me the same thing: “It’s unlikely we’ll see anything like an amicron or delta wave in the United States.”

If that sounds like good news, then it’s with some reservations. BA.2 seems unlikely to cause a new wave of disease and disruption so soon after Omicron wreaked havoc. But this does not mean that the country is now clean.

People are taking fewer precautions than ever before that will allow the virus to spread. There are people – the elderly, people with weakened immune systems, children under the age of 5 who are not yet eligible for vaccination – who may not have strong immunity or may not have immunity at all if they have BA.2. According to new data, the immunity created by recent vaccinations may not last long.

The next phase of the pandemic concerns more than just BA.2, Lesler said. This is “BA.2 + removing masks + lowering immunity”.

Even if BA.2 is unlikely to cause a nationwide wave, it still poses a danger

Perhaps the cases are underestimated as more people rely on home tests, the results of which they may not report to the local health department. BA.2 is also more likely to cause gastrointestinal disorders, and this may be misinterpreted as a gastric error. But hospitalization and death are less likely, and they are still steadily declining. Sewage samples may also show large amounts of virus when cases are exacerbated, even if more traditional observations show a decrease.

So why might BA.2 be a bit of a “fool,” as Mark Johnson, who heads the Missouri sewage monitoring program, described it to me?

The U.S. population has more immunity than ever before. About two-thirds of Americans received two injections of Covid-19 vaccine, and 30 percent received three injections. The recent wave of omicrons has also spread a lot of innate immunity that should provide protection from your cousin. From December 1 to March 1, more than 30 million cases of Covid-19 were reported.

Although BA.2 is more transmissible than the original strain of omicron, it does not seem to be able to escape the immunity conferred by a previous omicron infection, experts say. Vaccines also continue to provide a strong level of protection for most people.

Put it all together and, as Lesler said, BA.2 “doesn’t have enough power to overcome all the extra immunity”.

In some parts of the United States, where there have been several health restrictions and more relaxed attitudes that have allowed Omicron to tear the population apart, it is more likely that there is a lot of innate immunity to BA.2. This is one of the reasons why the US cannot replicate the UK experience with BA.2: the first amicron wave in America was much worse than in Britain in terms of death toll.

But in places that have hitherto been more cautious but are now easing the rules, larger pockets of the population could be intact by the amicron and therefore more susceptible to BA.2.

“We can have such strange phenomena when the places that cause the fury of the amicron can be relatively protected because they had a big amicron wave,” Lesler said. “But where the omicron was kept, we will most likely see a small bump. They have less protection from immunity, but from what they did, which they may stop doing. “

Different vaccination rates will also continue to play a role in how different communities live. “There are significant differences in vaccination rates and the like,” said William Hanej, an epidemiologist at Harvard University. “So I wouldn’t be surprised if in some places we see bumps that are more serious than others.”

Some people will also carry more risk than others because BA.2 is spreading. Older people are always at greater risk for serious complications of Covid-19, and although about 60 percent of the population over the age of 65 is amplified, new data published in the New England Journal of Medicine show that protection against infection is provided by vaccination. is fleeting.

People with weakened immune systems also tend to see fewer benefits from the vaccine, which puts them at greater risk. The Biden administration has allowed more people to receive additional vaccinations to reduce the risk for people over 50 and with immune diseases, but the additional immunity may be short-lived.

In addition, there are children under 5 who are still not eligible for vaccination against Covid-19. In general, they face a much lower risk of contracting the virus than the elderly. But this does not mean that their risk is zero. In particular, colored children are at greater risk for serious diseases and other rare complications, such as severe inflammation, which is sometimes associated with infection.

“Uncontrolled proliferation means greater morbidity and greater potential for long-term health consequences,” Ariana Plaine, professor of health policy at UNC, told me. “Due to the lack of vaccinations for children under 5, this is particularly worrying.”

Thus, Covid-19 will continue to affect, especially the most vulnerable, even if life begins to return to something close to normal.

“The challenge is how to find a balance where we can all follow sensible health measures … without undue panic,” al-Sadr said, referring to vaccinations and masks in crowded rooms in particular.

Experts also fear that in the long run a small ripple rather than a massive BA.2 wave could give a false sense of security. In a sense, we are lucky: this new variant takes effect shortly after the previous version of the virus with which it is associated, and for this reason has not shown a strong ability to evade existing immunity.

Our luck may hold back, but it is not guaranteed. In a presentation to the FDA this week, virologist Trevor Bedford outlined two possible scenarios for next year. In one scenario, BA.2 remains dominant, and future cases are driven by predictable factors such as seasonality and decreased immunity.

In this scenario, Covid-19 will not disappear, but the virus does not throw us at anything.

But another scenario is something similar to what happened with the first version of Omicron: there is a “wildly versatile” iteration of the coronavirus with a high frequency of attacks that threatens even people who have been vaccinated or previously infected.

Bedford said in his presentation that he believes the first scenario is more likely. But we were surprised before.

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