Saturday, February 19, 2022

As Covid death rate goes down, incidence of Omicron subvariant BA.2 goes up

As the national Covid death rate dropped to 4.2 per 100K per week on February 18, 2022, there has been a flurry of discussion about the BA.2 subvariant of Omicron:

BA.2 may cause more severe symptoms compared to omicron including text

“It might be, from a human’s perspective, a worse virus than BA.1 and might be able to transmit better and cause worse disease,” said Dr. Daniel Rhoads, section head of microbiology at the Cleveland Clinic in Ohio, according to CNN.

As BA.2 subvariant of Omicron rises, lab studies point to signs of severity including

New lab experiments from Japan show that BA.2 may have features that make it as capable of causing serious illness as older variants of Covid-19, including Delta. And like Omicron, it appears to largely escape the immunity created by vaccines. A booster shot restores protection, making illness after infection about 74% less likely. BA.2 is also resistant to some treatments, including sotrovimab, the monoclonal antibody that's currently being used against Omicron. The findings were posted Wednesday [16 Feb 2022] as a preprint study on the bioRxiv server, before peer review. Normally, before a study is published in medical journal, it is scrutinized by independent experts. Preprints allow research to be shared more quickly, but they are posted before that additional layer of review.


How Worried Should We Be About the BA.2 Omicron Subvariant?

Below is a conversation with Dr. Dan Barouch, a Harvard Medical School professor

In our preprint, which is under review at a major journal, we looked at Pfizer-vaccinated individuals as well as a cohort of Omicron-infected individuals. Similar to with BA.1, there was very little neutralization prior to a third boost of Pfizer. But after a third boost, neutralizing antibody titers [a test that measures the level of antibodies in a blood sample] came up strongly to both BA.1 and BA.2, still at substantially lower levels than the vaccine-matched strain. The neutralization titers between BA.1 and BA.2 were relatively similar. In our hands, there’s a slight trend toward lowering antibody titers against BA.2, about 1.3 to 1.4 fold. That’s a relatively minor difference; overall we found that antibody responses to BA.2 were roughly comparable, trending slightly lower, but roughly comparable to BA.1. That was true in vaccinated individuals and in people who were infected with Omicron BA.1. Those two data sets suggest that Omicron BA.2 does evade vaccines, but to a similar extent, not a greater extent as Omicron BA.1. Also it shows that people who are vaccinated and then infected with BA.1 have high neutralizing antibody titers against BA.2, suggesting there would be a substantial degree of cross-reactive natural immunity as well.

I can’t predict whether it will be a new surge or not, but it’s probably going to be driven more by increased transmissibility. It has similar, not fundamentally greater, ability to evade vaccines. The ability of BA.2 to become more dominant than BA.1 in certain populations appears to be more due to its increased transmissibility rather than some sort of brand new immune escape from vaccines.

The front page of the Feb.19, 2022 issue of the Courier-News carried some quotes from Dr. Reynold Panettieri of Rutgers.

When one (variant) does become more likely to induce infection, we're in a position to rapidly modify our vaccines and establish boosters for it (...) The fact is that so many people got infected by Omicron, and there could be carryover immunity that the likelihood of developing a completely resistant virus, I think, is going to be vanishingly low. But only time's going to tell."

As a comment to the above, one has the text

And like Omicron, it appears to largely escape the immunity created by vaccines.

As to boosters, the issue is not so much having a third (or fourth or whatever) booster, but rather the level of antibodies one has at the time of exposure to an entity with large viral shedding. And, one suspects the 65+ cohort will drop its antibody level faster than the 65- cohort. So, "establishing a booster" is only part of the story. The enhancement has a "date of expiration" on it. And none of the antibody talk deals with the subject of T cell immunity.

link for CDC data:

7 DAY DEATH RATE PER 100,000 4.2

TOTAL DEATHS 928,723 +2,226 New Deaths

Data as of 1:50pm (Eastern) on 18 Feb 2022

from the Courier News on 19 Feb. 2022


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