Having only been on the global radar since late November, early analysis around the world regarding the Omicron variant of concern (VOC) is providing insight into its characteristics and risks. Some preliminary laboratory analyses suggest that the Omicron variant could exhibit some resistance to SARS-CoV-2 vaccines. One study conducted by researchers in Germany (preprint) found that blood serum collected from fully vaccinated individuals had reduced efficacy in neutralizing the Omicron variant. The researchers tested sera from a variety of vaccinated patients, including those who received the Moderna, Pfizer-BioNTech, and AstraZeneca-Oxford vaccines, including some with heterologous combinations and some who received booster doses. The researchers observed reductions in neutralizing capacity on the order of 10-30 times, compared to the Delta variant. Additionally, sera from participants who received a heterologous combination of the AstraZeneca-Oxford and Pfizer-BioNTech vaccines exhibited “no efficacy against Omicron.” Pfizer-BioNTech announced (via press release) preliminary findings from their study on efficacy against the Omicron variant. This study identified sufficient neutralizing antibody titers among individuals who received 3 doses of the Pfizer-BioNTech vaccine, but there was a 25-fold reduction in neutralizing capacity for individuals who received only 2 doses of the Pfizer-BioNTech vaccine. Notably, these findings are based on the volume of neutralizing antibodies against the Omicron variant present in the sera, and not a direct assessment of efficacy against the variant. These studies provide initial insight into the efficacy of existing SARS-CoV-2 vaccines against the emerging Omicron variant, but we currently only have data from small, in vitro laboratory studies on which to base these analyses. The in vivo immune response varies widely, and it is unclear exactly how the current vaccines will function among the broader public or to what degree booster doses are necessary to provide sufficient protection. Current evidence suggests that existing vaccines may be less effective against the Omicron variant, but some experts indicate that fully vaccinated individuals would likely maintain some protection against severe disease. Larger studies among vaccinated individuals are necessary to gain the necessary insight. Dr. Mike Ryan, Director of the WHO’s Health Emergencies Programme, addressed speculation that the Omicron variant results in milder disease. He emphasized that while viruses tend to evolve to become more transmissible, the idea that a more transmissible virus results in milder symptoms is “an urban legend.” Even if the Omicron variant causes milder disease, increased transmission can put additional pressure on health systems. In addition to more patients with mild disease seeking care, milder disease that goes untreated can progress to more severe symptoms, and increased transmission can facilitate further mutations to the virus.
Scientists have identified a version of the SARS-CoV-2 Omicron (B.1.1.529) variant of concern (VOC) that cannot be distinguished from other variants using certain PCR tests that many public health officials use to quickly identify probable cases. The so-called “stealth” variant has many of the same genetic mutations as the originally identified Omicron VOC, but it lacks a certain deletion on the spike protein making it undetectable as the original Omicron lineage. Researchers have expanded the breadth of the B.1.1.529 lineage, creating 2 sub-lineages: BA.1 for the original VOC and BA.2 for the new outlier lineage. All of the usual tests are still effective at identifying the new lineage as SARS-CoV-2, but the new form of Omicron will make it more difficult to track Omicron infections because they need to be sequenced in genomic testing that takes a longer time to process. The new sub-lineage could vary from the original in transmission or disease severity, although it is too soon to say whether or if it behaves differently.
CSSE is reporting 49,775,621 positive cases in the U.S. and 796,215 deaths.
