Virendra Pandit
New Delhi: With the Delta variant of the SARS-CoV-2 virus causing the global pandemic Covid-19 reported in over 85 countries, the World Health Organization (WHO) warned on Thursday that the significantly more transmissible strain is likely to become a dominant lineage if the current trend continued.
In its Weekly Epidemiological Update released on June 22, the global health watchdog said the Alpha variant had been reported in 170 countries, territories, or areas, followed by Beta in 119, Gamma in 71, and Delta strain in at least 85 countries so far.
A new sub-variant, Delta Plus, has also been reported from some countries, including India.
The Delta variant (B.1.617.2) is being detected in new countries across all WHO Regions, 11 of which were newly reported in the past two weeks, the update said.
The four current ‘Variants of Concern’ (VOCs) being monitored closely–Alpha, Beta, Gamma, and Delta–are widespread and have been detected in all WHO regions.
The Delta variant is significantly more transmissible than Alpha and is expected to become a dominant lineage if current trends continue.
India reported the highest numbers of new Covid-19 cases, 441,976 over the past week (June 14-20, 2021), a 30 percent decrease as compared to the previous week. The highest numbers of new deaths were reported from India (16,329 new deaths; 1.2 new deaths per 100,000; a 31 percent decrease), according to media reports.
The South-East Asia Region reported over 600,000 new cases and at least 19,000 new deaths, a 21 per cent and a 26 percent decrease respectively compared to the previous week. Decreasing trends in the weekly case and death incidence in the region are predominantly associated with decreases reported in India.
Since the last detailed update on June 8, new evidence has been published on the phenotypic characteristics of the Delta variant. A study from Singapore showed that infection with Delta variant was associated with higher odds of oxygen requirement, intensive care unit (ICU) admission, or death, it said.
Also, a study in Japan “estimating the relative instantaneous reproductive number (a measure of transmission at a specific point in time) showed that the Delta variant was associated with greater transmissibility” when compared to the Alpha variant.
Compared with the variants circulating in Japan before December 2020, the relative instantaneous reproduction number for Alpha was estimated to be at 1.56 and for Delta 1.78. Overall, this study showed Delta was associated with 1.23 times higher transmissibility than Alpha.
The update also took note of two studies that have provided evidence of the effectiveness of Pfizer BioNTech-Comirnaty and AstraZeneca-Vaxzevria vaccines against the Delta variant. One study reports on the effectiveness of these vaccines against severe disease (hospitalization) due to Delta among persons over the age of 16 years in the United Kingdom.
Vaccine effectiveness estimates against hospitalization due to Delta and Alpha variants over 14 days post-second dose was estimated to be 96 per cent and 95 per cent respectively for Pfizer BioNTech- Comirnaty and 92 per cent and 86 per cent respectively, for AstraZeneca-Vaxzevria.
Single-dose effectiveness against hospitalisation over 21 days after immunization remained high for Pfizer BioNTech-Comirnaty at 94 per cent against Delta and 83 per cent against Alpha. The effectiveness of one dose of AstraZeneca-Vaxzevria against hospitalization was similar for Delta and Alpha variants.
A second study from Scotland found that two doses of Pfizer BioNTech-Comirnaty were 83 per cent and 79 per cent effective against symptomatic disease and infection due to Delta, respectively, over 14 days after receipt of the second dose in persons 15 years and older.