Eric Topol posted on his blog about yet another new variant, XBB.1.5 that is apparently becoming more prevalent in some geographic areas. It appears to me that there is not enough sequencing data right now to know for sure exactly what it is happening with this variant.
>>>New York is the bellwether for what is happening with XBB.1.5 and it doesn’t look good with a marked rise in hospitalizations
, especially among seniors, in recent weeks as this variant has been taking hold. Of course, other factors are likely contributing such as waning of immunity, indoor/holiday gatherings, cold weather, lack of mitigation. But it is noteworthy that New York’s Covid hospital admission rate is the highest since late January (and also exceeds the summer 2021 Delta wave, but with some ambiguity as to how hospitalization were categorized then and now). . . . So we don’t know for sure how much of this is being driven by XBB.1.5, but it doesn’t look favorable. <<<
It looks like XBB.1.5 is rapidly becoming more prevalent (I believe the CDC numbers are estimates, so it's not clear exactly how many cases are caused by XBB.1.5).
>>>Dec 30 (Reuters) - Over 40% of COVID-19 cases in the United States are now caused by the highly contagious Omicron XBB.1.5, data from the U.S. Centers for Disease Control and Prevention showed on Friday, with the subvariant doubling from the previous week.<<<
>>>There’s no indication it causes more severe illness
than any other omicron virus, Dr. Barbara Mahon, director of CDC’s Coronavirus and Other Respiratory Viruses Division, told NBC News.
While overall Covid hospitalizations are rising around the country, areas such as the Northeast that have seen high levels of the new variant have not experienced a disproportionate increase in hospitalizations, Mahon said.<<<
About 40% of confirmed U.S. Covid cases are caused by the XBB.1.5 strain, up from 20% a week ago.
The nbcnews.com article has a link to a letter published in the NEJM, which found that the bivalent booster had a better neutralizing antibody response to XBB than the original boosters (XBB.1.5 was not included)(and, of course, it didn't look at T cell response).
>>>Persons who received either one or two monovalent Covid-19 vaccine boosters had much lower neutralization activity against omicron subvariants (especially against BA.2.75.2, BQ.1.1, and XBB, which contain the predicted escape mutation R346T) than that against the WA1/2020 strain. Persons who received the BA.5-containing bivalent booster had better neutralizing activity against all omicron subvariants (especially against BA.2.75.2, BQ.1.1, and XBB) than those who received either one or two monovalent boosters, even though the neutralization GMT against WA1/2020 was similar in the cohort that received the two monovalent boosters and the cohort that received the bivalent booster. These responses are consistent with recent observations in persons with breakthrough omicron infection showing broadened neutralizing activity against omicron subvariants.5
Limitations of this study include the small cohort size, differences in age among the cohorts, the unknown effect of previous exposure to SARS-CoV-2, and comparison of the vaccines at a single time point. These serologic data show an overall neutralization benefit with bivalent booster immunizations.<<<
The NEJM study should probably be taken with a grain of salt because there were only 35 people total (three cohorts of 12, 11, and 12 people).