It has been a quiet period for new scientific information despite much happening with Omicron - which has now been detected in over 130 countries and is the dominant variant in several (including South Africa, Denmark, UK, Japan, India, Australia, France, USA). It is reported that case numbers have declined in South Africa sufficiently for them to consider the Omicron wave over, and there are possible signs of a plateau beginning in UK. Despite very high case numbers in the worst affected countries, the pattern with hospitalisations is less consistent. In the USA there have been calls for consideration of hospitalisation numbers as the prime statistic rather than case numbers (which reached 1 million in one day). Those regions with very high case numbers also are experiencing enormous levels of work absence due to isolation of close contacts, which strains health systems as well as the airline industry. In some locations, systems and equipment for COVID testing are struggling to meet demand.
This letter to JAMA from South Africa has really interesting data from the most recent (Omicron) wave – Maslo et al: https://jamanetwork.com/journals/jama/fullarticle/2787776
Notably: of patients treated, 31% were admitted (vs around 70% in previous waves), and 32% had respiratory conditions on admission (vs around 68% previously); and duration of hospital stay was markedly shorter (average 3 days vs 7-8 days in previous waves) with much less need for oxygen (18% vs 74-82), ICU (18.5% vs 30-42%). Finally the incidence of ventilation (1.6% vs 8-16%) or death (2.7% vs 20-29%) was far lower, but numbers were small and some of the 4th wave group were still in hospital at the time of publication.
Of those admitted to hospital, 66% were unvaccinated – but over half of the population had previous exposure to SARS-CoV-2 at this time.
These findings have to be interpreted with some caution as this group was much younger (average 36 vs in 50’s previous waves) with much fewer co-morbidities (23% vs over 50% previous waves), and many of this 4th wave group were admitted for other reasons with an incidental finding of COVID-19.
In NEJM an article, of which the main findings were forwarded previously - 70% neutralisation against Omicron vs 93% for Delta, with Pfizer vaccination, but strong restoration after a 3rd dose at least in the short term. Nemet et al: https://www.nejm.org/doi/pdf/10.1056/NEJMc2119358
And also reported previously from South Africa were the main findings from Collie et al in NEJM: https://www.nejm.org/doi/full/10.1056/NEJMc2119270
Some 28% of those admitted with COVID during the Omicron period were fully vaccinated, compared with 8% during the prior period. The computed effectiveness of vaccination against hospital admission was 70% for the Omicron compared with 93% previously.
See also this Danish study from last week, Lyngse et al: https://www.medrxiv.org/content/10.1101/2021.12.27.21268278v1.full
They found a secondary attack rate in households of 31% compared with 21% for Delta, and despite the immune escape of the variant, there was significant benefit of boosters beyond full vaccination. “Our findings confirm that the rapid spread of the Omicron VOC primarily can be ascribed to the immune evasiveness rather than an inherent increase in the basic transmissibility”
Studies (pre-print) continue to show most (monoclonal) antibody treatments to be ineffective against Omicron, as discussed here in Nature: https://www.nature.com/articles/d41586-021-03829-0 and also here by Boschi et al: https://www.biorxiv.org/content/10.1101/2022.01.03.474769v1.full.pdf
I will not be reporting the weekly CDC level changes in these updates this year, but you can reference the latest travel advisory levels at any time from CDC here: COVID-19 Travel Recommendations (COVID-19 THN webpage).
IATA Medical Advisor