Scientists claim Delta variant has greater ability to evade immunity in recovered patients

The different variants of SARS-CoV-2 have so far successfully tested the effectiveness of vaccines against COVID-19. And in accordance with the concern that has aroused the scientific community since its appearance, we now know that the Delta variant, first identified in India in December 2020, is more contagious than the original SARS-CoV-2 and is better able to evade the previous or natural immunity, present in recovered patients, that is, they have already been infected with the virus from their lineage that emerged in Wuhan.

As estimated by researchers at the Mailman School of Public Health at Columbia University using a computer model, the mutation that emerged in India is about 60% more contagious than the original Wuhan coronavirus. Besides, can escape immunity from a previous infection almost half the time, the same researchers warned. Compared to Delta, Beta and Gamma are less transmissible but better able to evade immunity. Compared to the original virus, the Iota variant is more deadly in the elderly.

The conclusions of three variant studies of SARS-CoV-2 have been published on the prepress server medRxiv before publication in a peer-reviewed journal.

Wan Yang, PhD, assistant professor of epidemiology and lead author of the studies noted that “New variants of SARS-CoV-2 have become widespread, but currently vaccines are still very effective in preventing serious illnesses caused by these infections, so get vaccinated if you haven’t. “

“It is important that we closely monitor the spread of these variants to guide ongoing preventive measures, vaccination campaigns and evaluation of vaccine effectiveness. the expert analyzed. More fundamentally, to limit the emergence of new variants and end the COVID-19 pandemic, We need global efforts to immunize all populations in the world and continue to use other public health measures until enough of the population is protected by immunization. “

According to researchers, the Delta variant (B.1.617.2) is 10-20% more transmissible than Alpha, another highly contagious variant of concern. Additionally, unlike Alpha, which has been shown to cause minimal immune evasion, Delta can also evade previous immunity in about half of individuals previously infected with the ancestral strain.

These results are in line with UK estimates that Alpha is about 1.5 times more likely to cause infection. (combining 10-20% increase in transmissibility with <~ 50% increase in susceptibility due to immune escape from previous natural infection and, to a lesser extent, vaccination).

Compared to Beta and Gamma, the variant Delta is more transmissible but less able to evade immunity. The drop in Delta cases in India in early May is likely due to the implementation of public health measures and weather conditions. The monsoon season (June-September) and winter (December-January) could see increased transmission of the virus. The Delta variant was first detected in December 2020 and has spread to 142 countries as of August 10.

Researchers developed computer models of COVID-19 to estimate changes in transmissibility and immune escape for each variant, based on case and mortality data for the country where each variant appeared. The models took into account the under-detection of infection, seasonality of the disease, concurrent non-pharmaceutical interventions and mass vaccination.

“New variants of SARS-CoV-2 such as B.1.526 could increase transmissibility, evade previous immunity and increase the severity of the disease. Early preparation and close monitoring of SARS-CoV-2 variants and their epidemiological characteristics is crucial for the response to the COVID-19 pandemic, as it continues to pose a threat to global public health.», They concluded.

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