How Does the COVID Delta Variant Compare?
In late 2020, a variant of COVID-19 was detected in India that began to quickly spread.
Soon after it received the label “Delta,” it started to become the predominant strain of COVID-19 in countries of transmission. It spread faster than both the original disease and other variants, including “Alpha” that had taken hold in the UK.
Now the COVID-19 pandemic has essentially become the Delta pandemic, as the variant accounts for more than 90% of global cases.
But how does the COVID-19 Delta variant differ from the original disease? We consolidated studies as of September 2021 to highlight key differences between COVID-19 and the dominant variant. Sources include the CDC, Yale Medicine, and the University of California.
COVID-19 vs COVID-19 Delta Variant
At first glance, infections caused by the Delta variant are similar to the original COVID-19 disease. Symptoms reported from patients include cough, fever, headache, and a loss of smell.
But studies showed that the difference was in how quickly and severely patients got sick:
- Spread rate: How quickly the infection spreads in a community (based on the R0 or basic reproductive number). The Delta variant spread 125% faster than the original disease, making it potentially as infectious as chickenpox.
- Viral load: How much of a virus is detectable in an infected person’s blood, with higher loads correlating with more severe infections. Delta infections had a 1000x higher viral load.
- Virus detectable: How long after exposure a virus is detectable in an infected person’s blood. Delta infections were found to be detectable four days after exposure, faster than the original disease (six days).
- Infectious period: How long an infected person has the capability to pass on the virus to other people, from the first time they were exposed. Delta infections were contagious for longer than traditional COVID-19 infections, at 18 days compared to 13 days.
- Risk of hospitalization: How much more or less likely is an infection going to require hospitalization for treatment? Infections caused by the Delta variant were twice as likely to cause hospitalization compared to the original disease.
One other important finding from studies was that the existing COVID-19 vaccines helped against Delta infections.
The CDC found that approved vaccines reduced the rate of infection by 5x and the rate of hospitalization by 29x in a breakthrough case. They also found that overall efficacy against infection can wane over time, however, and at-risk people might require a booster vaccine.
What About Other COVID-19 Variants?
Delta is just one of many COVID-19 variants tracked by health officials, but it’s the one we know the most about.
That’s because reliable statistics and information on diseases requires thousands of cases for comparisons. We know a lot about Delta (and the once-dominant UK strain Alpha) because of how widespread they became, but there haven’t been enough cases of other variants to reliably assess differences.
As of September 2021, WHO was tracking 20 COVID-19 variants around the world with different classifications based on potential severity:
- 14 Variants under monitoring (VUM): Variants that are deemed to not pose a major global health risk, or no longer pose one.
- 2 Variants of Interest (VOI): Variants that affect transmissibility, virulence, mutation, and other virus characteristics, and are spreading in clusters.
- 4 Variants of Concern (VOC): Have similar characteristics to VOI but are further associated with a global risk.
Most of the current variants of interest and concern were first identified and labeled in late 2020, though 2021 variants are showing up as well.
|Label||Designation||Documented Origin||Earliest Identified Date|
|Alpha||Variant of Concern||UK||September 2020|
|Beta||Variant of Concern||South Africa||May 2020|
|Gamma||Variant of Concern||Brazil||November 2020|
|Delta||Variant of Concern||India||October 2020|
|Lambda||Variant of Interest||Peru||December 2020|
|Mu||Variant of Interest||Colombia||January 2021|
Should you be worried about all of these variants? For the most part, a lack of cases to provide clear information also reflects that they’re equivalent to or weaker than traditional COVID-19 infections.
But it’s important to note that our understanding of diseases and variants becomes more nuanced and accurate over time. As research continues over a longer timeline and over a wider database of cases, expect information on COVID-19 variants (and any disease) to become more concrete.
Innovation in Virology: Vaccines and Antivirals
Vaccine development has grown six-fold since 1995. Learn how virology, the study of viruses, is driving innovation in the healthcare industry.
Innovation in Virology: Vaccines and Antivirals
The COVID-19 pandemic affected millions of people worldwide and brought renewed focus to virology—the study of viruses.
However, impact made by viruses extends far beyond the SARS-CoV-2 virus that causes COVID-19. There are 24 viruses that have each infected more than 80 million people globally, from hepatitis to influenza.
In this graphic from MSCI, we uncover innovation in vaccines and antivirals and the related market opportunities.
What is a Virus?
A virus is a microscopic infectious agent that replicates within living cells. It may cause disease in its host. New viruses can emerge at any time as a result of mutation, or when viruses transfer from animals to humans.
Through virology, scientists are continuously finding new ways to fight against infectious diseases. Two main types of anti-infectives are available: vaccines and antivirals.
Rapid Innovation in Vaccines
Vaccines are substances designed to prevent people from getting infected with a disease or experiencing serious symptoms.
The number of vaccines has increased dramatically over the last three decades. From 2020 to 2021 alone, the number of approved vaccines or clinical candidates jumped by 13%.
|Year||Vaccines Approved or in Development|
Data is a snapshot in time and reflects all vaccines ever approved (and not taken off the market) plus all vaccines in development as of the noted year (for which a trial has not been canceled).
Not only that, it’s possible to have shorter approval timelines. COVID-19 vaccines were approved within 11 months, much more quickly than the 2000-2020 average of 10 years.
In the time between an outbreak and vaccine development, antivirals can play a vital role.
Antivirals: The Second Line of Defense in Virology
Antivirals are drugs that slow or prevent the growth of a virus and treat disease symptoms. They are especially important tools for diseases that do not have an associated vaccine.
In 2021, there were nearly six times as many approved antivirals as there were in 1995. Not only that, antiviral uses have grown to include the potential prevention and treatment of HIV, COVID-19, and a number of other diseases.
in the U.S.
The potential prevention (prophylaxis) and treatment of the same virus are counted as separate uses. Data is cumulative and reflects all antivirals ever approved (and not taken off the market) and all reasons ever approved for using antivirals (that have not been rescinded).
Innovation in virology—and the potential for future developments—is leading to a growing industry.
Expanding Market Opportunities
With opportunities growing and approval times shortening, more companies are entering the market.
|Year||Companies Developing Vaccines/Antivirals|
Data is a snapshot in time and reflects all companies developing vaccines or antivirals as of the noted year. If a company stops being active in the space or ceases to exist, they are removed from the total.
As they work to develop new vaccines and antivirals, companies are conducting clinical trials for many diseases beyond COVID-19 such as respiratory infections and sepsis.
Virology is leading to a number of groundbreaking technologies and therapies, transforming healthcare along the way.
Explore the MSCI Virology Index now.
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