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Although the above chart suggests that the latest COVID wave - sparked by Omicron - is losing steam, this week's WHO Epi report contains multiple reminders that testing, and reporting, of cases has diminished around the globe and that `These trends should be interpreted with caution. . . '.
For political, and practical reasons, many countries have shifted the way they count, and report cases, making comparisons to earlier numbers difficult. Additionally, in Mainland China - where we're seeing a growing number of outbreaks - reporting is always a bit suspect.
What is apparent is that in highly vaccinated countries, hospitalizations and deaths due to COVID have dropped. Regions where the uptake of the vaccine - particularly among the elderly - is lower, are still seeing substantial morbidity and mortality from the virus.
From this week's Epi report:
Data as of 10 April 2022
Globally, during the week of 4 through 10 April 2022, the number of new COVID-19 cases and deaths has continued to decline for a third consecutive week, with over 7 million cases and over 22 000 deaths reported, a decrease of 24% and 18% respectively, as compared to the previous week (Figure 1).
All regions reported decreasing trends in the number of new weekly cases and deaths (Table 1). As of 10 April 2022, over 496 million confirmed cases and over 6 million deaths have been reported globally.
These trends should be interpreted with caution as several countries are progressively changing their COVID-19 testing strategies, resulting in lower overall numbers of tests performed and consequently lower numbers of cases detected.
At the country level, the highest numbers of new weekly cases were reported from the Republic of Korea (1 459 454 new cases; -29%), Germany (1 019 649 new cases; -26%), France (927 073 new cases; -3%), Viet Nam (453 647 new cases; -43%), and Italy (447 322 new cases; -8%).
The highest numbers of new weekly deaths were reported from the United States of America (3 682 new deaths; -9%), Republic of Korea (2 186 new deaths; -6%), the Russian Federation (2 008 new deaths; -15%), Germany (1686 new deaths; +6%), and Brazil (1 120 new deaths; -22%).
This week's report also offers the following brief update on variants, including the inclusion of the BA.4 and BA.5 Omicron subvariants we discussed last week. It is too early to know what - if any - impact these new variants will have on the course of the pandemic.
Geographic spread and prevalence of VOCs
The Omicron variant remains the dominant variant circulating globally, accounting for nearly all sequences recently reported to GISAID. Among the 379 278 sequences uploaded to GISAID with specimens collected in the last 30 days i , 376 082 (99.2%) were Omicron, 125 (<0.1%) were Delta and 2 961 (0.8%) sequences were not assigned to a Pango lineage.
These trends should be interpreted with due consideration of the limitations of surveillance systems, including differences in sequencing capacity and sampling strategies between countries, as well as laboratory turn-around times for sequencing and delays in reporting.
Omicron VOC
WHO continues to monitor several descendent lineages under the Omicron VOC, including BA.1, BA.2, BA.3 as well as now BA.4 and BA.5 . It also includes BA.1/BA.2 circulating recombinant forms, such as XE. The full list can be found here https://cov-lineages.org/lineage_list.html
A small number of sequences of BA.4 and BA.5 descendent lineages have now been detected in a few countries. Both have additional mutations in the Spike region (S:L452R, S:F486V) and unique mutations outside of Spike. The S:L452R and S:F486V mutations are associated with potential immune escape characteristics. In addition, the majority of BA.4 and BA.5 sequences have the 69-70 deletion responsible for S gene target failure (SGTF) in some PCR assays. This may prove useful for surveillance purposes in places where BA.2 is dominant, as the 69-70 deletion is largely not present in BA.2 sequences.
WHO is working with scientists to further assess the characteristics of these lineages and their public health implications. WHO recommends countries to continue surveillance, where possible, and rapid data sharing on publicly available databases.
And lastly, the WHO addresses the notion that the pandemic may be waning in their latest Rapid Risk Assessment. While some countries are currently seeing reduced impact from the virus, others - particularly those with low vaccine uptake - continue to face considerable challenges.
Despite a reduction in SARS-CoV-2 testing observed since the beginning of 2022 in many Member States, the COVID-19 pandemic continues with intense transmission and high levels of death primarily among unvaccinated at-risk populations. The highly transmissible Omicron variant of concern has rapidly replaced all other circulating variants in almost all countries in which it has been reported, and has become dominant globally.
Omicron’s properties of immune escape have been associated with the rapid and almost synchronous increase in the global incidence of COVID-19 cases reported until the end of January 2022. A further increase observed at the beginning of March was driven primarily by a delayed increase in case incidence in the Western Pacific Region and a rebound in the number of new cases reported in the European Region. This trend was likely due to a combination of factors, including the predominance of the Omicron Pango lineages BA.1, and then BA.2, with a transmission advantage over other Omicron lineages; relaxation of public health and social measures (PHSM); and waning of humoral immunity following vaccination and/or prior infection. The recent detection of emerging recombinants of the Delta-Omicron and Omicron descendent lineages requires ongoing close monitoring.
Unlike previous waves, the most recent wave due to Omicron can be characterized by a decoupling between the number of cases, hospitalizations (particularly for intensive care) and deaths in many countries. However, data continue to show that those who are unvaccinated remain at higher risk of severe disease following infection with Omicron as compared to those who have been vaccinated. Despite the reduction in severity, the massive increases 6in cases with Omicron have led to large numbers of hospitalizations, putting further pressure on healthcare systems, and in some countries, similar or higher numbers of deaths when compared to previous peaks.
While vaccine effectiveness (VE) wanes against Omicron for all disease outcomes as compared to other VOCs following the primary vaccination series, VE estimates for Omicron remain the highest for severe disease. Furthermore, there is evidence that a booster dose substantially improves VE for all outcomes; however, more data are needed to characterize the duration of this protection.
Over 11 billion vaccine doses have been distributed globally. Nevertheless, substantial inequities remain, with only 11% of those in low-income countries (LICs) having completed the primary series; and major differences among regions, with vaccination coverage ranging from 82% in the Western Pacific Region to 13% in the African Region.
There is particular concern about reaching the most vulnerable populations who remain unvaccinated, particularly those of older age and those with comorbidities. Globally, an estimated 35% of those aged 60 years and over are awaiting completion of the primary vaccination series. Despite low vaccination coverage in the African Region, the most recent estimates of combined seroprevalence (vaccine and infection-derived humoral immune response) were 72.6% (95% CI: 71.7-73.5%). Considering the low vaccine coverage, such seroprevalence estimates highlight the extent of SARS-CoV-2 transmission across the Region.
WHO Emergency Use Listing (EUL) approved diagnostic tests, including nucleic acid amplification tests (e.g. polymerase chain reaction (PCR) assays) with more than one viral target or antigen-detection rapid diagnostic tests (Ag-RDTs), remain effective at detecting Omicron infection, including BA.1 and BA.2. WHO is concerned that during recent months, some countries have significantly reduced SARS-CoV-2 testing, despite widespread availability of diagnostic tests. Unless robust surveillance systems are retained, countries may lose the ability to accurately interpret epidemiological trends, implement the appropriate measures necessary to reduce transmission and monitor and assess the evolution of the virus.
Despite current high rates of transmission of SARS-CoV-2, many countries have dropped most PHSM without following a layered or staged approach to relaxation. This can lead to the erosion of public trust and PHSM may not be easily re-implemented should the future need arise, for example following the emergence of a new VOC. Each country faces different circumstances based on the epidemiological situation and the context. WHO has published an updated Strategic Preparedness, Readiness and Response Plan to End the Global COVID-19 Emergency in 2022 which outlines future scenarios of COVID-19 and how the current strategy needs to be adjusted taking into account the difficulties posed by the pandemic in the light of the many other public health and global challenges.
This is particularly apparent during other emergencies including the war in Ukraine and protracted conflicts in many other countries.
The confidence in the available information on the global public health risk remains moderate. There are still gaps in knowledge about the phenotypic impact of emerging SARS-CoV-2 variants and recombinants; the long-term duration of infection and vaccine-derived protection, particularly against severe disease and hospitalization; and the impact of lifting and changing PHSM on transmission, hospitalization and mortality.
While it is understandable for regions currently experiencing lulls in transmission, hospitalizations, and deaths to want to return to normal, we've literally seen 3 new variants (B.1.1.529, BA.1.1, BA.2) emerge and rise to dominance over the past 4 months.
As long as COVID continues to reinvent itself at breakneck speed, it is too soon to declare victory.
