There have been numerous news reports about three studies that just came out (see, e.g., AP link below). The first looked at hospitalization and death rates, the second looked at Emergency Department/Urgent Care/hospitalizations, and the third looked at infection rates. There's a lot of data in the three studies and I have not read them completely.
From the AP article:
>>>The first study
looked at hospitalizations and emergency room and urgent care center visits in 10 states, from August to this month. . . . Officials have stressed the goal of preventing not just infection but severe disease. On that count, some good news: A third dose was at least 90% effective at preventing hospitalizations for COVID-19, both during the delta and omicron periods, the study also found. The second study
focused on COVID-19 case and death rates in 25 states from the beginning of April through Christmas. People who were boosted had the highest protection against coronavirus infection, both during the time delta was dominant and also when omicron was taking over. . . . [according to the third study] Three shots of the Pfizer and Moderna vaccines were about 67% effective against omicron-related symptomatic disease compared with unvaccinated people. Two doses, however, offered no significant protection against omicron when measured several months after completion of the original series, the researchers found. <<<
One thing I have been curious about is how accurate the PCR "no S gene = omicron" result is with regards to detecting omicron. Based on the third study, it appears to be reasonably accurate, although it might undercount omicron relative to delta somewhat:
>>>For this analysis, an Omicron case was defined as presence of S
-gene target failure (SGTF) in the test sample and a Delta case as absence of SGTF in the test sample. All samples that were determined by the processing laboratory to be SARS-CoV-2 positive had Ct values for at least 2 of the N
, and S
genes. SARS-CoV-2–positive samples were considered to have SGTF if they had Ct values for the N
genes but not for the S
gene; otherwise, samples were considered not to have SGTF.
SGTF may serve as a proxy for the presence of the Omicron variant in samples tested with the TaqPath COVID-19 Combo Kit assay because of the presence of deletions in the S
-gene region for Omicron that are not present in Delta2
; the deletions lead to S
-gene–negative results in Omicron lineages BA.1 and B.1.1.529 but not the majority of Delta samples. While levels of non-Delta circulating variants other than Omicron remain low, samples with SGTF may be presumed to be Omicron.22
At the time of this analysis 99.9% of sequenced samples in the US prior to the emergence of Omicron were Delta.4
To validate the use of SGTF as a proxy for Omicron in the ICATT data, the frequency of SGTF was examined in a randomly selected subset of tests with positive results that were sequenced during the same period as the analysis. The sequenced subset was drawn from the complete database of test results from the laboratory, including tests not eligible for the main analysis. Sequencing data were not available for most cases included in the main analysis, which is why SGTF was used as a proxy. The sensitivity of SGTF for detecting Omicron (B.1.1.529 or BA.1 lineage) was 83.4% and the specificity was 99.2% (eTable 1 in the Supplement
Based on my super quick initial scan, it appears to me that the the first two studies included data from December when omicron started to become dominant, but these studies didn't look at actual omicron vs delta rates in the subjects of the studies (i.e. based on my initial scan, the third study is the only one that did). The third study showed that there was a mix of delta and omicron in the samples they looked at between 12/10/21 and 1/1/22:
>>>A total of 70 155 tests from 4666 sites on samples collected between December 10 and January 1 across 49 states met inclusion criteria (Figure 1
), including 23 391 cases (13 098 Omicron; 10 293 Delta) and 46 764 controls (Table 1
Also based on a brief initial scan, I didn't see a lot of information in the studies concerning possible prior infection. The third study excluded people who had tested positive during the previous 90 days, but I didn't see anything in the results that took into account positive tests more than 90 days prior to the samples.
NEW YORK (AP) — Three studies released Friday offered more evidence that COVID-19 vaccines are standing up to the omicron variant, at least among people who received booster shots. They are the first large U.S.