‘COVID-19 herd immunity unlikely to slow transmission in coming months’

Expect third wave in the US in winter

By DTE Staff
Published: Thursday 29 April 2021

The United States, the country affected most by the novel coronavirus disease (COVID-19) pandemic, is staring at a third wave next winters. Latest forecast by Institute for Health Metrics and Evaluation (IHME), University of Washington, warned it would be ominous not only for the US, but also for the rest of the world.

“Herd immunity is unlikely to be a factor in slowing transmission in the coming months, even with vaccination campaigns ramping up,” IHME Director Christopher Murray said.

The assessment was based on the evolution of new contagious variants of SARS-CoV-2 — the novel coronavirus. The forecasts, widely used and accepted, took into account two new variants — B.1.351 and B.1.1.7.

Murray said people needed much higher levels of immunity to resist a more contagious variant and that also in winters.

More to it, he raises the grim forecasts based on the fact that vaccines are yet to be fully assessed on their efficacy. According to IHME’s forecasts, 38 per cent of the US would be immune to the virus by May 1:

As important is the fact that we do not know if the vaccines work to block infection even though they prevent severe disease — IHME’s model currently assumes, based on limited data, that vaccines’ effectiveness in blocking infection is only 50 per cent of their effectiveness in preventing severe disease.

Emergence of B.1.351 significantly influenced IHME’s forecasts besides mobility returning to near normal levels in vaccinated localities. According to an April 29 IHME analysis:

The US is predicted to see approximately 654,000 total deaths by May 1 and a resurgence of the virus in the spring in some states, including California and Florida, rather than a continued decline.

Many US states have not imposed physical-distancing norms despite high daily infection numbers. The IHME forecasts have taken into consideration this factor as well to gauge the future pathway of the COVID-19 infection: “In a worst-case scenario, there is also the possibility of a third wave next winter.”

Murray said: “People will need to continue taking precautions even once they are vaccinated, because of the potential for more contagious variants to spread.”

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