Here’s what we know about the BA.2 Omicron subfactor driving a new COVID-19 wave

After a brief two-month plateau, COVID-19 cases are back on the rise again in the United States, driven by Omicron BA.2 and its more transmissible descendants. The spike has alarmed experts, as more people are getting rid of their masks and returning to pre-pandemic activities.

Between April 1 and April 24, New COVID-19 cases jump 75 percent, mostly due to BA.2; This is the alternative now It accounts for nearly 75 percent of COVID-19 cases In the United States while hospitalization Still at its lowest Since the start of the pandemic, they’ve also been trending upwards nationally. and cases of COVID-19 among residents and staff of a nursing home It is rising again after falling for about three months.

“It is likely that the continuous transmission of BA.2 is related to both Increased transmission of the virus Along with reducing epidemiological restrictions,” says Dan Baruch, an immunologist at Harvard Medical School who directs the Center for Virus and Vaccine Research at Beth Israel Deaconess Medical Center. “Both are clearly contributing to the current boom.”

At the same time, national vaccination rates have stopped. Just 45.6 percent of the US population has received a booster dose By dose, and in at least 10 states, mostly in the South, more than a third of the population remains unvaccinated. This is particularly alarming because early data suggests that BA.2 may cause more serious disease than the original form of Omicron.

The first Omicron wave arrived when many people in the United States had already been vaccinated, so it appeared to cause less serious disease and gained a reputation for being mild, says Ben Cowling, an epidemiologist at the University of Hong Kong. But the word “mild” was only associated with the severe disease caused by the previously dominant delta variant.

Melinda Maldonado, a strategic communications expert in Toronto, received the triple vaccine when she contracted an unprecedented infection in December 2021, during the height of the Omicron wave in Canada. He left her bedridden for weeks, and three months later she still suffers from debilitating fatigue, brain fog, and cognitive confusion.

“When people say ‘moderate,’ they mean you don’t die, like you don’t end up in the intensive care unit,” Maldonado says. “For me, that wasn’t cute.”

Now, there is evidence that Variant BA.2 is more contagious From the first form of an omicron, Produces more virus particles when infected, causing long-term COVID-19 cases.

Why does BA.2 cause more serious illness?

The earlier form of Omicron, called BA.1, was more contagious than previous variants, but caused less lung damage than Delta because It stays mostly in the upper airwayssays Guowei Wei, a mathematician and molecular biologist at Michigan State University, whose AI model was Expect Omicron to be highly contagious. However, the current crop of vaccines protects against BA.1, which in most cases has caused less intense Disease is one of the previous variables between the Those who have been vaccinated and who have some immunity from a previous infection.

studies showed that the overall risk of severe outcome from omicron infection was lower than in Delta. But the risk of hospitalization among children under 10 years of age It did not differ significantly between Omicron and DeltaAnd Omicron infection led to higher hospital admissions From very young children.

Another study showed that in children, Omicron caused three times more hospitalizations for respiratory infections than the previous variants.

Now it appears that BA.2 may be more concerning. In the UK, the number of cases recorded during the current BA.2 surge is much lower than what they saw during the Omicron wave in late December 2021 – but Number of hospital admissions It is almost equal.

One study that has not yet been peer-reviewed Suggests why BA.2 may be more severe. A team led by Kei Sato, a University of Tokyo virologist, created a synthetic version of BA.2 in the lab, finding that it grows faster in cells lining the nasal passage and has a greater tendency to attack the lungs. This virus is similar to BA.2 too Cause more severe illness in hamsters than its BA.1 counterpart.

The research suggests that mutations in the BA.2 spike protein – the part of the virus that attaches to cells – enable it to evade antibodies from a previous BA.1 infection.

else Study by Cowling and his team which have not yet been peer-reviewed show that in Hong Kong, the severity of BA.2 is as bad as it was for the original SARS-CoV-2 variant for unimmunized people of any age.

“In Hong Kong, and now in Shanghai, I don’t think so [BA.2] “As mild as people think,” Cowling says.

Do Vaccines Still Work for BA.2?

Available data shows that currently approved vaccines will prevent severe infection and hospitalization from COVID-19, More so in cases of BA.2 from BA.1.

Denmark and South Africa currently have high levels of immunity in their populations resulting from vaccination and infection, respectively. But data from both countries showed that there was no significant difference in severity between BA.2 and BA.1 infections. Re-infection with different subtypes of omicronalthough in highly vaccinated Denmark, it was rare and mainly affects younger unvaccinated individuals.

Boost doses also show a lot of hope for protecting people of all forms of omicron.

Various studies have shown that a third dose of the vaccine, or superinfection, can occur Activating the immune system’s memory to produce antibodies It works well with all variants, including Omicron. Baruch of Harvard University led a study showing that a The third dose of the vaccine is a must To produce adequate levels of antibodies against BA.2, just as required For complete protection against BA.1.

Centers for Disease Control and Prevention (CDC) Now Recommend a fourth dose of the vaccine For people 50 years of age or older, four months after the third dose; And Extra dose for those with a weakened immune system, such as cancer patients. In a study that has not yet been peer-reviewed, a The fourth dose significantly reduced penetration infection Among health care workers at high exposure risk, even at the height of the first Omicron wave. In addition to the stimulant doses Significantly reduces a person’s chances of transmitting the virus.

By contrast, the Hong Kong study revealed that results can be severe among unvaccinated people with any of the Omicron variants, including BA.2.

More variables on the horizon

As SARS-CoV-2 continues to spread and transform globally, facilitated by pandemic fatigue, Recombinant variables continue to be configured; The recently discovered XE subvariable is a mixture of BA.1 and BA.2 that is beginning to spread; Cases of XE are relatively rare but have grown enough that UK Health Security Agency estimates It is 10% more contagious than BA.2.

Meanwhile, a new descendant of BA.2 called BA.2.12.1 spreads more quickly, causing 20 percent of all cases in the United States Within a month of its date Discovery in early March. Previous estimates show that BA.2.12.1 spreads faster than previous strains It can be better at staving off antibodies to the immune system.

“There are really many new versions of Omicron, not just two. And in some cases, they seem to outperform even BA.2,” says Harvard’s Baruch.

All of this means the United States “needs to recharge its vaccination program” to avoid a potential spike in fall and winter, says Saad Omar, an epidemiologist who directs the Yale Institute for Global Health in Connecticut.

In addition to vaccinations, Masks have been shown to be effective in reducing the risk of contracting COVID-19both by reducing Spread of viral material from an infected person and by Reduce the chances of infection. And experts stress that avoiding infection should really be the goal: The effects of COVID-19, including the set of symptoms known collectively as COVID-19, can be debilitating.

“I thought if I got COVID it would be a cold because that’s the dominant narrative,” Maldonado says. “I want people to consider the risks when they think about opening things and not using a mask, because you don’t know if it could be you.”