COVID-19: The Delta Variant
30.08.2021
To continue prioritizing global health research and monitoring of COVID-19, specific variants of Interest (VOIs) and Variants of Concern (VOCs) are frequently identified and characterized. This characterization- with reference to SARS-CoV-2, the virus that causes COVID-19- ultimately informs the ongoing response to the pandemic. Most viruses mutate and change with time- sometimes, the new variants have changes that make little or no difference in the properties of the virus. However, some changes are capable of altering the properties of the virus such as ease of spread, severity of symptoms, performance of vaccines, therapeutic drugs, diagnostic devices, or other social and public health markers.
A newly identified Delta variant of SARS-CoV-2, has gained popularity in recent times. The variant, which originated from India and was identified as a variant of concern in May 2021, is linked to the second wave of the COVID-19 pandemic and has now spread to over 100 countries. The Delta variant h as become the dominant strain globally as it continues to spread in various countries irrespective of vaccination coverage. In a matter of months after its identification, the virus was isolated in more than 98 countries, making it the most dominant variant globally particularly in India, Scotland, the U.K., Israel and the United States. Over 83% of COVID-19 cases being reported in the U.S. can now be attributed to the Delta variant. As a VOC, the Delta variant has significant changes that may influence it’s properties.
Fundamentally, three questions drive research around newly identified variants:
- How contagious is the Delta variant?
- Is the Delta variant more dangerous than other variants of concern?
- Will vaccines remain protective against the Delta variant?
To answer the above questions, much research is underway while some facts have already been established through scientific observations including:
Transmission: The Delta variant has proven to be more contagious than other variants. The Centres for Disease Control and Prevention confirms that the Delta variant accounted for more than 80% of new cases in the United States in July 2021.
Symptoms: Good news here as the symptoms associated with the Delta variant are not more severe than the previously identified variants. In fact, the symptoms of the Delta variant appear to be the same as the first variant of COVID-19, even though the virus grows more rapidly and people get sick faster, especially younger people. According to surveys in the U.K., where the Delta variant accounts for most current COVID-19 cases, symptoms caused by the Delta variant appear a little different than other strains, but not necessarily more severe. Fever, headache, sore throat and runny nose are common, while cough and loss of smell are rare. Other surveys report more serious symptoms, including hearing impairment, severe gastrointestinal issues and blood clots leading to tissue death and gangrene. Research is ongoing to determine if infection with the Delta variant is associated with increased hospitalization and death.
Vaccination: Most vaccinated people are either asymptomatic or mildly symptomatic if infected with the Delta variant. Their symptoms are limited to those of a common cold, such as cough, fever or headache and loss of smell. On the other hand, unvaccinated people may suffer symptoms that lead to hospitalization if infected. By inference, vaccines are considered highly effective in preventing severe COVID-19 infection and disease, including that of the Delta variant. A research from the U.K. suggests that full vaccination with the Pfizer-BioNTech COVID-19 vaccine confers about 90% protection and prevents symptomatic infection and severe disease by the delta variant. Additionally, a Canadian research showed that one dose of the Moderna COVID-19 vaccine results in about 85% prevention against symptomatic COVID-19 virus infection and severe disease caused by the delta variant. Finally, data released by Johnson & Johnson, showed that the Janssen/Johnson & Johnson COVID-19 vaccine is 85% effective at preventing severe disease with the COVID-19 virus caused by the delta variant.
Although the Delta variant is currently the most prominent strain of COVID-19, the Lambda variant isolated in South America is also emerging. Health experts maintain that a significant portion of the population must be vaccinated to confer herd immunity and for things to completely go back to normal. As long as most people across the world are unvaccinated, new strains of the virus will continue to emerge and potentially create new problems.
Current strategies and measures recommended by WHO continue to protect against virus variants identified since the start of the pandemic. Evidence from multiple countries indicate that public health and social measures (PHSM), including infection prevention and control (IPC) measures, have remained effective in reducing COVID-19 cases, hospitalizations and deaths. National and local authorities are therefore encouraged to continue strengthening existing PHSM and IPC measures as well as surveillance and sequencing capacities.
Reducing transmission through effective disease control measures and avoiding infections in animal populations, are crucial aspects of the global strategy to reduce the prevalence of mutations that have negative public health implications. In collaboration with partners, expert networks, national authorities, institutions and researchers, World Health Organization continues to characterize, monitor and asses the evolution of SARS-CoV-2.