A SARS-CoV-2 variant with traits similar to that of the Delta variant-;enhanced transmissibility and an ability to infect people who had previous infections/vaccination-;will cause a more severe pandemic with more infections and breakthrough infections/reinfections than variants with either trait alone, according to a mathematical model created by researchers at Harvard T.H. Chan School of Public Health.
The study, which was published online on November 19 2021 in Cell, could aid researchers and public health professionals understand the significance of new and existing variants and design customized public health strategies to various scenarios based on the variation’s characteristics.
So far, evidence of immune escape-;the ability of a mutation to escape the immune system and cause outbreaks or reinfections-;has been a red flag. Our research suggests that it’s more of a yellow flag-;this isn’t a huge deal by itself. However, when it’s paired with increased transmissibility, it could be a important issue.”
Mary Bushman, co-author of the Cell paper, is a postdoctoral research fellow at the Department of Epidemiology at Harvard Chan School
Variants of the SARS-2 virus in the wild have emerged as the COVID pandemic continues to progress. Some of these variants have become dominant strains which have increased the frequency and severity of the diseases, such as the Alpha and Delta versions. Other variants, such as Beta, have failed to take root or had a significant impact on the course of the pandemic. To understand the effects that certain factors would influence a pandemic Bushman developed a model which simulates how pandemics fueled by hypothetical variants would affect people who are using various combinations of masking, physical distancing and vaccinations.
The analysis included several variants of SARS-CoV-2. These included combinations of both the two traits: enhanced transmission (similar to the Alpha variant) and partial immune escape (similar to the Beta variant); enhanced transmissibility with partial immunity escape (similar to the Delta variant) and a variant with neither characteristic. The analysis also factored in how certain variables, like physical distancing, masking, or vaccinations would affect the pandemic’s trajectory. Researchers looked at the total number and percentage of infections prevented through vaccinations for each scenario.
Bushman and his team found that a variant that has enhanced transmission could be more dangerous than one that can partially evade immune system. A variant with both traits could lead to more infections, reinfections and breakthrough infections than a variant that does not have either trait.
The model suggests that vaccinations is extremely beneficial in the event of Delta-like variants. This is due to the fact that vaccinations will stop more cases than a more transmissible virus strain could cause. Also, because breakthrough infections are milder and therefore, mortality overall should be substantially decreased.
“It’s really important that people understand that the increasing incidence of variants like Delta which makes the importance of vaccination all the more crucial,” said Bill Hanage an associate professor of epidemiology and co-author of the Cell paper. “Even if we cannot eliminate the virus, we can ensure that those who are exposed to it have the most effective preparation. Moreover, an increased risk of transmission means that there will be more cases of infection in the absence of vaccination, which means that more people will benefit from it.”
Bushman, M., and. (2021) Population impact of SARS CoV-2 variants with enhanced transmissibility , and/or partial immune escape. Cell. doi.org/10.1016/j.cell.2021.11.026.
Content Source: https://www.news-medical.net/news/20211121/Delta-like-SARS-CoV-2-variants-with-enhanced-transmissibility-may-cause-a-more-severe-pandemic.aspx