Experts: More than 70% of Americans need additional vaccine shots for full protection from Omicron

·West Coast Correspondent
·9 min read

According to the U.S. Centers for Disease Control and Prevention, nearly 60 percent of Americans are now “fully vaccinated” against COVID-19, having received either one shot of the Johnson & Johnson vaccine or two shots of Pfizer or Moderna.

But experts are starting to believe that the heavily mutated Omicron variant — which has already been detected in at least 11 states — could reverse at least some of America’s progress on immunity as it spreads across the country, leaving nearly three-quarters of the population newly susceptible to breakthrough cases or reinfection.

“Omicron is an immune escape variant that breaks through immunity caused by prior infection and/or vaccination,” Dr. Tom Wenseleers, a professor of biology and biostatistics at Belgium’s Katholieke Universiteit Leuven, concluded Thursday after reviewing the latest data from South Africa, where the variant was first detected and where it’s currently driving a near-vertical spike in infections and hospitalizations. “People getting a booster ASAP is the best protection for now, at least until specifically adapted vaccines” arrive.

The latest on the Omicron variant

What that means, according to Dr. Eric Topol, director of the Scripps Research Translational Institute, is that “three shots” of Pfizer or Moderna — or one shot of Johnson & Johnson, plus a booster — should be the new standard for full vaccination. (For people with prior COVID, he added, one or two shots “establishes potent hybrid immunity.”)

But instead, the U.S. is “going the wrong way” on immunizations, Topol told the Washington Post. “We’re at 59 [percent] and fading” as protection wanes for people without boosters.

To prepare for Omicron, the U.S. needs to pick up the pace — and rethink what full protection entails. "Right now, officially, fully vaccinated equals two shots of the mRNA and one shot of the J&J, but without a doubt, that could change," Dr. Anthony Fauci, the nation’s top infectious disease expert, said last month. "That's on the table for discussion.”

To be clear: Both the vaccines and the virus train the immune system’s T-cells and B-cells to block severe disease in the future, and Omicron is unlikely to dodge those underlying defenses. As a result, experts believe that most people who’ve already received two vaccine shots or recovered from COVID will retain significant protection against hospitalization and death.

Dr. Anthony Fauci, President Biden's chief medical adviser, delivers an update on the Omicron variant of  COVID-19 at the White House on Dec. 1.
Dr. Anthony Fauci, President Biden's chief medical adviser, delivers an update on the Omicron variant of COVID-19 at the White House on Dec. 1. (Photo by Anna Moneymaker/Getty Images)

But what’s also becoming clear as Omicron overruns South Africa is that it can evade existing antibodies — the initial barriers that “prevent SARS-CoV-2 from using its spike to dock onto vulnerable cells, or earmark the virus for violent destruction” before it infects its host, as The Atlantic recently put it. Our most important antibodies target three sites on SARS-CoV-2’s spike protein; Omicron carries mutations in all three regions, and each of them resembles an earlier mutation known to thwart our immune defenses.

The numbers from South Africa are sobering. Before Omicron was detected on Nov. 23, the country was averaging about 300 COVID cases per day; roughly 2 percent of COVID tests were coming back positive. On Friday — just 10 days later — South African officials reported more than 16,000 cases and a test positivity rate of over 24 percent. Omicron, they said, now accounts for more than three-quarters of infections nationwide.

The “current wave of cases is so steep, it’s climbed as high in 20 days as Delta got in 42,” explained John Burn-Murdoch, a data journalist at the Financial Times.

Initially, hospitalizations, a lagging indicator, did not seem to be increasing at a faster rate than during earlier waves driven by the Delta and Beta variants, raising hopes that Omicron might be less likely to trigger serious illness than its predecessors.

But that is changing as hospitals backfill their admissions numbers, and now South Africa’s hospitalization curve is steepening as well. In fact, the country’s week-over-week increase in hospital admissions is already higher than it was at the start of prior waves, according to data from South Africa’s National Institute for Communicable Diseases.

Making matters worse, Burn-Murdoch continued, the “admissions line now [reflects the] cases line a week ago, not today” — and the “Omicron wave in Gauteng,” the epicenter of the South African outbreak, “currently skews very young." This, he added, would "push the case-hospitalization rate down, but only while cases remained concentrated among the young."

In short, hospitalizations are likely to keep accelerating along with the number of cases, and may accelerate even more as the variant spreads to older South Africans.

A health worker administers a dose of COVID-9 vaccine on Thursday as part of the vaccination campaign in Cuenca, Ecuador.
A health worker administers a dose of COVID-9 vaccine on Thursday as part of the vaccination campaign in Cuenca, Ecuador. (Photo by Agencia Press South/Getty Images)

Researchers are still trying to determine whether Omicron is more transmissible or virulent than Delta; studies are underway, and they’ll reveal more this month. But with Omicron cases now doubling in South Africa roughly every three days, scientists there are already saying the variant appears to be spreading more than twice as quickly as Delta — and that at least part of the reason is because the risk of reinfection with Omicron is roughly 2.4 times higher than with the original version of the virus, according to their estimates. 

“It is actually really striking how quickly it seems to have taken over,” Juliet Pulliam, the director of an epidemiological modeling center at the University of Stellenbosch in South Africa, told the New York Times after her team quantified a rapid uptick in reinfections among people who had tested positive for the virus at least 90 days earlier.

Natural immunity alone, in other words, does little to stop Omicron from spreading.

Corresponding data is not yet available for breakthrough infections in people who received either two or three vaccine doses, and there’s reason to believe vaccine-induced immunity may hold up better against Omicron because its antibodies tend to bind to more parts of the virus than those induced by prior infection. 

Either way, experts expect Omicron to evade vaccine-induced antibodies more often than any variant to date — and because boosters lift antibody levels to new heights, while also broadening their reach, they also expect a lot more evasion in people who haven’t received a third jab than in those who have.

It has been clear for months that the Pfizer and Moderna vaccines’ original 90-plus percent effectiveness against COVID infection and hospitalization has worn off over time and in the face of the hypercontagious Delta variant — but that it can be restored, almost instantly, with a third shot. (For Johnson & Johnson recipients, the CDC now recommends a second shot of any COVID vaccine two months after the first.)

“All adults need a 3rd shot irrespective of the Omicron variant,” Dr. Ashish K. Jha, dean of the Brown University School of Public Health, tweeted Thursday. “If we really want to get the virus under control, of course we need to get the unvaccinated to become vaccinated. But we also need vaccinated people to have full protection.”

Omicron makes that need more urgent.

A passenger off a flight from South Africa is tested for the coronavirus at Amsterdam's Schiphol Airport on Dec. 2.
A passenger off a flight from South Africa is tested for the coronavirus at Amsterdam's Schiphol Airport on Dec. 2. (Photo by Pierre Crom/Getty Images)

To date, 198 million Americans have been “fully vaccinated.” But 146 million of them received their last shot more than six months ago — the point at which the CDC recommends an mRNA booster to restore full protection.

Only 44 million Americans have received their booster shot.

That means that more than 100 million Americans should have received a booster by now but haven’t. Meanwhile, the number of unboosted-but-overdue Americans rises by 600,000 to 700,000 each day as people who got their second jabs back in June cross the six-month threshold and their immunity continues to wane.

Experts say all of those people are no longer fully protected — especially against Omicron. In fact, if you were to recalculate the full U.S. vaccination rate to exclude every vaccinated American who has crossed the six-month mark without getting boosted, only 28 percent of Americans would clear the bar. 

Restoring full protection won’t be easy. Before Thanksgiving, about 700,000 Americans were getting boosted each day — the same as the number of fully vaccinated Americans who were crossing the six-month “waning” threshold. Little progress was being made.

Since then — since Omicron shook things up — booster uptake has risen to slightly over 1 million doses per day. Yet even at that faster pace, it would take more than four months to close the booster gap and restore America’s full-protection rate to 60 percent.

Meanwhile, Omicron has already infiltrated the U.S., and many questions remain. The U.S. isn’t South Africa; there, only 24 percent of the population has received two vaccine doses. Far from fizzling out, as had already happened in South Africa when Omicron was first detected, the Delta variant is currently causing an average of more than 94,000 new U.S. cases per day — substantial competition for any novel variant. The more people who are currently infected with a different, highly infectious strain, the fewer hosts are available for a newcomer to latch onto.

So can Omicron outcompete Delta here as well? Is a 60-percent vaccination rate enough? If not, what level of vaccination will successfully slow the spread when natural immunity no longer seems to play much part? Can unvaccinated Americans finally be convinced to roll up their sleeves as a result? How much protection will boosters actually provide? Will bespoke Omicron vaccines eventually be necessary? How will post-infection treatments such as monoclonal antibodies and antiviral pills perform?

The bottom line, however, is simple: The more infections Omicron causes, the more school and work and business will be disrupted — and the more Americans will fall ill and die.

Right now, boosters — along with new vaccinations — are the best tool for minimizing Omicron infections. The U.S. will never get to zero COVID; living with the virus is the future. But that future will be a lot less painful — and a lot more normal — if as many people as possible are as fully protected as possible from infection.


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