Scientists Estimate 73% of US Population May Be Immune to SARS-CoV-2 Omicron Variant
Clinical laboratory scientists should also know experts warn that ‘herd resistance’ is more likely than ‘herd immunity’ due to low vaccination rates in many parts of the world
Scientists estimate 73% of the US population may be immune to the SARS-CoV-2 omicron variant. Whether the nation is approaching “herd immunity” against the disease, however, remains open to debate, the Associated Press (AP) reported. These estimates are relevant to medical laboratories doing serology tests for COVID-19, as different individuals will have different immune system responses to COVID-19 infections and vaccines.
More than two years into the COVID-19 pandemic in the United States, the CDC’s COVID Data Tracker shows the number of daily cases dropped to fewer than 50,000 as of March 4, 2022, after reaching a high of 928,125 on January 3, 2022.
Meanwhile, the seven-day death rate per 100,000 people stands at 2.78. That’s significantly above the seven-day death rate reached last July of .45, but well below the 7.21 mark recorded on January 13, 2021.
“We’re clearly entering a new phase of the pandemic,” William Morice, II, MD, PhD, Department of Laboratory Medicine and Pathology at Mayo Clinic in Rochester, Minn., told KARE11, an NBC affiliate.
Is Herd Immunity Achievable?
According to the AP, an estimated 73% of the US population is likely to be immune to the Omicron variant due to vaccination or natural immunity from contracting the disease. That calculation was done for the media outlet by the Institute for Health Metrics and Evaluation (IHME) at the University of Washington in Seattle. The IHME anticipates immunity to Omicron could rise to 80% this month, as more people receive vaccination booster shots or become vaccinated.
Despite those optimistic totals, however, Don Milton, MD, DrPH, Professor of Environmental Health at the University of Maryland School of Public Health, suggests achieving herd immunity to COVID-19 and its variants may no longer be possible.
“Herd immunity is an elusive concept and doesn’t apply to coronavirus,” he told the Associated Press (AP).
Milton maintains populations are moving toward “herd resistance,” rather than “herd immunity.” This will transform COVID-19 into a permanent fixture with seasonal outbreaks similar to influenza.
Herd Immunity Varies, according to the WHO
Because antibodies that developed from vaccines—or natural immunity from a previous infection—diminish over time, waning protection means even those boosted or recently recovered from COVID-19 could be reinfected. In addition, vaccination rates vary widely around the world. Our World in Data estimates only 13.6% of people in low-income countries had received one dose of the COVID-19 vaccine as of March 7, 2022.
The World Health Organization (WHO) points out that herd immunity levels vary with different diseases. Herd immunity against measles requires about 95% of a population to be vaccinated, while the threshold for polio is about 80%.
“The proportion of the population that must be vaccinated against COVID-19 to begin inducing herd immunity is not known. This is an important area of research and will likely vary according to the community, the vaccine, the populations prioritized for vaccination, and other factors,” the WHO website states.
Living with COVID-19
Nonetheless, the US appears to be moving into a new “normal” phase of living with the disease.
In an interview with Reuters, US infectious disease expert Anthony Fauci, MD, Director of the National Institute of Allergy and Infectious Diseases (NIAID) acknowledged a need for returning to normal living even though portions of the population—immunocompromised individuals and the unvaccinated, including children under age five who are not eligible for vaccination—remain vulnerable to more severe COVID-19.
“The fact that the world and the United States—and particularly certain parts of the United States—are just up to here with COVID, they just really need to somehow get their life back,” Fauci said. “You don’t want to be reckless and throw everything aside, but you’ve got to start inching towards that. There’s no perfect solution to this.”
Most states have lifted coronavirus-related restrictions, including masking requirements. As COVID-19 cases drop in California, Gov. Gavin Newsom put in motion a plan called SMARTER (Shots, Masks, Awareness, Readiness, Testing, Education, and Rx) that no longer responds to COVID-19 as a crisis, but instead emphasizes prevention, surveillance, and rapid response to future variant-based surges in cases.
“We have all come to understand what was not understood at the beginning of this crisis, that there’s no ending, that there’s not a moment where we declare victory,” Newsom told USA Today.
Mayo Clinic’s Morice agrees. “It can’t be out of sight, out of mind, per se, but it at least gives us hope that we can get back to some level of normalcy here over the course of the year,” he said.
Since clinical laboratories played a critical role in assay development and COVID-19 testing, medical laboratory leaders should continue monitoring COVID-19 as it moves from pandemic to endemic status due to high vaccination rates and advances in treatment options.
The COVID-19 pandemic has raised awareness among healthcare consumers as well, about the critical role laboratory medicine plays in modern medicine and healthcare. Medical laboratory leaders and pathologists would be wise to amplify this message and stress the importance of clinical laboratory testing for many diseases and healthcare conditions.
—Andrea Downing Peck
Related Information:
Estimated 73% of US Now Immune to Omicron: Is That Enough?
Model Estimates 73% of Americans Immune to Omicron Variant
Fauci Says Time to Start ‘Inching’ Back Toward Normality
Is Omicron Leading US Closer to Herd Immunity against COVID?
