Only 20% of Americans have efficient safety towards Omicron an infection
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In a latest analysis paper printed as an accepted manuscript within the Clinical Infectious Diseases journal, scientists analyzed the inhabitants immunity towards pre-Omicron and Omicron extreme acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) variants in U.S. counties and states up till December 1, 2021.

Study: Population immunity to pre-Omicron and Omicron SARS-CoV-2 variants in US states and counties by December 1, 2021. ​​​​​​​Image Credit: NIAID


In the United States (US), almost 48 million SARS-CoV-2 circumstances and 780,000 coronavirus illness 2019 (COVID-19)-related deaths had been documented by December 1, 2021. In addition, an additional 26 million infections and 100,000 mortalities had been reported within the US between December 1, 2021, and February 1, 2022.

Furthermore, the emergence of the SARS-CoV-2 Omicron variant highlights the need to determine areas of biggest vulnerability and the way steady viral evolution could diminish efficient immunity. Achieving excessive ranges of neighborhood immunity is vital for minimizing COVID-19 mortality and morbidity. COVID-19 and its vaccination each contribute to community-level SARS-CoV-2 immunity.

Estimates of neighborhood immunity on the native degree are essential for figuring out the dangers of constant COVID-19 transmission. Based on blood donation info, state-level estimates of vaccine- and infection-induced SARS-CoV-2 seroprevalence have been printed, with estimates various from 63.7% in Mississippi to 91.7% in Connecticut for May 7 2021. While these estimates supply a direct seroprevalence measure throughout the examine teams, systemic variations amongst blood donors and the widespread public could affect them. Furthermore, these datasets don’t present estimates on the county degree or replicate the fading of safety.

About the examine

The present examine assessed the immunological publicity and efficient immunity towards future SARS-CoV-2 an infection for every US county and state from 2020 to 2021 and the way this has altered after the SARS-CoV-2 Omicron variant emerged. The researchers used modeled estimates of cumulative SARS-CoV-2 infections on the county and state ranges and documented protection for preliminary and booster COVID-19 vaccination. Further, they calculated the joint distribution of previous SARS-CoV-2 an infection and vaccination utilizing the survey knowledge.

Daily SARS-CoV-2 an infection and vaccination knowledge estimates had been synthesized using a Bayesian mannequin. In addition, the estimates of comparative vaccination charges conditional on the standing of an infection had been used to find out the proportion of the neighborhood with 1) SARS-CoV-2 immunological publicity (SARS-CoV-2-infected or vaccinated), 2) efficient immunity towards COVID-19, and three) efficient immunity towards extreme sickness, for every US county and state from January 1, 2020, to December 1, 2021, utilizing the Bayesian framework.

Furthermore, the authors estimated efficient neighborhood immunity towards SARS-CoV-2 an infection and extreme COVID-19 with time and efficient immunity towards the Omicron variant whereas accounting for immunological escape, utilizing knowledge on the time-course of vaccine- and pure infection-induced immunity.


The examine outcomes demonstrated that the estimated proportion of the US inhabitants with a SARS-CoV-2 vaccination or an infection historical past as of December 1, 2021, was 88.2%. 

In US states, efficient immunity towards COVID-19 from pre-Omicron variants was between 27.6% and 40.4%, decrease than the proportion immunologically uncovered, adjusting for the waning of neighborhood immunity. Moreover, efficient immunity towards the SARS-CoV-2 Omicron pressure an infection on December 1, 2021, was 21.8% nationwide, starting from 14.4% in West Virginia to 26.4% in Colorado, after controlling for immune evasion and waning. The Omicron variant’s introduction and takeover lowered efficient immunity towards SARS-CoV-2 an infection by about 26.2% to 37% amongst all US states. Effective immunity towards extreme COVID-19 related to Omicron was 61.2% throughout the US, starting from 53% in Vermont to 65.8% in Colorado.

The researchers said that by December 1, 2021, greater than three-quarters of the US inhabitants had prior SARS-CoV-2 immunological publicity by both an infection or vaccination. Besides, 50% of the inhabitants exhibited efficient immunity towards an infection from beforehand circulating SARS-CoV-2 variants, whereas only a fifth had efficient immunity towards Omicron variant an infection.


Overall, the current examine evaluated the shared distribution of SARS-CoV-2 and COVID-19 vaccination in every county and state of the US for the reason that begin of the epidemic and the evolution of immunity over time.

The examine findings depicted that on December 1, 2021, over 80% of the US inhabitants had earlier immune publicity to SARS-CoV-2 through an infection or vaccination. Yet, simply 20% of the inhabitants had efficient immunity towards an infection with the immune-evading Omicron variant. The group famous that the estimations of efficient immunity towards COVID-19 and extreme sickness throughout the inhabitants reported on this analysis present helpful info for evaluating the native SARS-CoV-2 menace in states and counties within the US.

Additionally, the authors talked about that present and novel SARS-CoV-2 variants most likely proceed to flow into as a result of neither pure an infection nor vaccination confers lasting immunity towards COVID-19. Hospitalizations per capita had been the main focus of latest Centers for Disease Control and Prevention (CDC) pointers for native COVID-19 surveillance. Nevertheless, neighborhood outbreaks have to be monitored utilizing indicators like testing quantity and wastewater knowledge monitoring.

Journal reference:

  • Fayette Klaassen, Melanie H Chitwood, Ted Cohen, Virginia E Pitzer, Marcus Russi, Nicole A Swartwood, Joshua A Salomon, Nicolas A Menzies; Population immunity to pre-Omicron and Omicron SARS-CoV-2 variants in US states and counties by December 1, 2021; Clinical Infectious Diseases, 2022, ciac438, DOI:,

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