Delta Variant Is 60% More Contagious Than Original COVID Virus and Can Escape Immunity

The Delta variant is more contagious than original SARS-CoV-2 and better able to escape previous immunity, modeling studies of coronavirus variants show.

Researchers from Columbia University’s Mailman School of Public Health used a computer model to estimate that the Delta variant is about 60 percent more contagious than the original SARS-CoV-2 virus and can provide immunity from previous infection about half the time. escape. Compared to Delta, Beta and Gamma are less transmissible, but more capable of escaping immunity. Compared to the original virus, Iota is more deadly for older adults.

Findings from three studies of SARS-CoV-2 variants are published on the medRxiv pre-print server prior to publication in a peer-reviewed journal.

“New variants of SARS-CoV-2 are widespread, but currently vaccines are still very effective at preventing serious illness from these infections, so please get vaccinated if you haven’t already,” says Wan Yang, PhD, assistant professor of epidemiology and lead author of the studies. “It is important that we closely monitor the spread of these variants to guide ongoing preventive measures, vaccination campaigns and assessment of vaccine efficacy. More fundamentally, to limit the emergence of new variants and end the COVID-19 pandemic, we need global efforts to vaccinate all populations worldwide and continue to use other public health measures until a sufficient proportion of the population is vaccinated. is protected.”

Delta

The researchers estimate that the Delta variant (B.1.617.2) is 10 to 20 percent more transmissible than Alpha, another highly contagious variant of concern. Furthermore, unlike Alpha which has been shown to cause minimal immune evasion, Delta is also able to evade previous immunity in about half of individuals previously infected by the ancestral strain. These findings are in line with UK estimates that Alpha is approximately 1.5 times more likely to result in infection (combined with a 10-20% increase in transmissibility with <∼50% increase in susceptibility due to immune evasion for previous natural infection and, to a lesser extent, vaccination). Compared to Beta and Gamma, the Delta variant is more transmissible, but less able to escape immunity. A decline in Delta cases in India that began in early May was likely due to the implementation of public health measures and weather conditions. The monsoon season (June-September) and winter (December-January) can lead to higher virus transmission. The Delta variant was first detected in December 2020 and has spread to 142 countries as of August 10.

Alpha, beta and gamma

In addition to Delta, Alpha (B.1.1.7), Beta (B.1.351), and Gamma (P.1) are the other three SARS-CoV-2 variants currently classified by the WHO as variants of concern that have spread worldwide . The researchers estimate that Alpha is about 50 percent more transmissible than the original virus, but only nominally capable of escaping the protection afforded by previous infection with the original SARS-CoV-2 variant. Beta has about a 30 percent increase in transmissibility and 60 percent immune escape, and Gamma has about a 40 percent increase in transmissibility and 50 percent immune escape.

Jota

Iota (B.1.526), ​​an interesting WHO variant, is estimated to be 15-25 percent more transmissible than the original SARS-CoV-2 and somewhat immune-evasive (0-10%). The study, which focused on New York City, where the Iota variant emerged in November 2020, found that Iota significantly increased the risk of death compared to pre-existing variants in older adults: by about 45 percent among 45-64-year-olds. year-olds, 80 percent among 65-74 year-olds and 60 percent among over-75s in the period November 2020-April 2021.

computer model

The researchers developed computer models of COVID-19 to estimate the changes in transmissibility and immune escape for each variant, based on case and mortality data from the country where each variant originated. Models were responsible for underdetection of infection, seasonality of disease, concomitant non-pharmaceutical interventions, and mass vaccination.

References:

“Epidemiological Features of the B.1.526 SARS-CoV-2 Variant” by Wan Yang, Sharon K. Greene, Eric R. Peterson, Wenhui Li, Robert Mathes, Laura Graf, Ramona Lall, Scott Hughes, Jade Wang, and Anne Fine , August 7, 2021, medRxiv.
DOI: 10.1101/2021.08.04.21261596

“COVID-19 pandemic dynamics in India and impact of the SARS-CoV-2 Delta (B.1.617.2) variant” by Wan Yang and Jeffrey Shaman, June 25, 2021, medRxiv.
DOI: 10.1101/2021.06.21.21259268

“Epidemiological features of three SARS-CoV-2 variants of care and implications for future pandemic consequences of COVID-19” by Wan Yang and Jeffrey Shaman, May 21, 2021, medRxiv.
DOI: 10.1101/2021.05.19.21257476

Additional authors can be found on individual study pages. The research was supported by the National Institute of Allergy and Infectious Diseases (AI145883, AI163023), the National Science Foundation Rapid Response Research Program (DMS-2027369) and a grant from the Morris-Singer Foundation. The Iota study was also supported by the NYC Department of Health and Mental Hygiene.