The COVID-19 omicron BA.4 and BA.5 subvariants have rapidly increased in prevalence in New England in recent weeks.
Data from the US Centers for Disease Control (CDC) shows that the subvariants first arrived in New England in mid-April, but began to grow exponentially by the end of April. may.
The data shows that together the subvariants accounted for around 6.5% of cases at the end of May, before rising to around 12.4% by the end of the first week of June. The subvariants then jumped to account for around 15.4% of cases the following week, and finally reached around 24% at the end of last week.
BA.2.12.1 is still the most prevalent variant regionally and nationally, accounting for 68.3% of infections in New England and 56% nationally, but it is possible that BA.4 and BA.5 represent an increasing share of cases over the coming weeks, similar to other parts of the country.
In an email to Boston.com on Wednesday, David Hamer, professor of global health at Boston University (BU), wrote that BA.4 and BA.5 have many of the same mutations that made the original variant d ‘omicron so concerning, but that they also have new mutations that may make them more transmissible.
Hamer said they had a mutation that might make it easier for them to attach to human cells, and another that might help them better evade immune responses.
Still, Hamer said, there’s no evidence that these variants cause more severe disease, so they’re not likely to increase hospitalization rates except in people who haven’t been vaccinated or haven’t. had a natural infection.
Matthew Fox, an epidemiologist at BU, agreed with Hamer’s assessment of transmissibility and the lack of evidence that these variants cause more severe disease, and said they did not appear to have a higher mortality rate. than the original omicron variant.
“If, however, this version is able to evade immunity, we could see more infections than in the last wave, and that could lead to more hospitalizations just because there are more people infected,” he wrote to Boston.com in an email.
On Wednesday, a Harvard University and Beth Israel Deaconess Medical Center study published in the New England Journal of Medicine found that these variants can evade immune responses better than previous variants.
The study found that the BA.4 and BA.5 variants were three times more resistant to neutralizing antibodies than BA.1 and BA.2, which are already much more resistant to neutralizing antibodies than the original COVID-19 virus. .
For this reason, the researchers wrote, BA.4 and BA.5 could cause substantial flare-ups even in populations with high vaccination rates and natural immunity to BA.1 and BA.2, although vaccination should still provide protection against serious illnesses.
Hamer said based on this new information, he believes there could be a substantial increase in infections in New England this summer or early fall.
“This raises concerns,” Fox wrote. “But it’s also a small sample, so I think we have to wait and see what happens at the population level.”
Overall, he said, it’s too early to tell what impact BA.4 and BA.5 will have as they increase in prevalence across New England.
Fox and Hamer said BA.4 and BA.5 have been observed in South Africa and several European countries so far. Hamer said those countries have seen a gradual increase in cases due to the new variants, but have not seen large waves of infections.
Fox added that infection rates are generally lower in the summer due to higher temperatures and people going outside more, but said there was really no way to know for sure.
“I don’t think there’s too much to worry about yet, but…I think we should prepare,” he wrote. “People should think about what steps they are prepared to take if infection rates increase.”
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