Feb. 3 (UPI) -- Hopes that the United States may be approaching herd immunity against COVID-19 may be dashed by the emergence of new variants of the virus, though expanding infection-control measures could solve that problem, experts said Wednesday.
With 26.4 million confirmed cases, and up to 10 times as many actually infected, the 32.8 million people vaccinated against the virus nationally through Tuesday could mean the country is close to herd immunity, according to immunologist David C. Montefiori.
Herd immunity means that most of the population would be protected from COVID-19, either through prior infection or vaccination.
However, because the virus is still "replicating," or spreading, in many parts of the country, the virus will continue to mutate, as evidenced by new strains first identified in England, South Africa and Brazil, Montefiori said.
Prior infection with the more common strain of COVID-19, which originated in Wuhan, China, or vaccination may not be as effective at providing protection against these new strains, which could also delay widespread immunity, he said.
"All viruses mutate, and the more opportunity they have to replicate, the more opportunity they have to mutate," said Montefiori, director of the Laboratory for AIDS at Duke University Medical Center.
"The only way to prevent virus mutation is by stopping replications -- so by stopping virus from spreading, you can prevent it from mutating," he said during a conference call with reporters Wednesday.
Part of the effort to stop the spread of COVID-19 -- and its ability to replicate and mutate -- could be double-masking, according to infectious disease specialist Dr. Becky Smith, who spoke during the same call.
Earlier this week, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, suggested that the U.S. Centers for Disease Control and Prevention could recommend that people wear two face coverings in public, as opposed to one, in the near future.
Although people in some parts of the country "are just getting around to wearing one mask" covering the nose and mouth to prevent virus spread, adding a second mask makes sense, said Smith, an associate professor at Duke School of Medicine.
Wearing a medical-grade mask over the nose and mouth significantly reduces the release of airborne virus particles and limits transmission, and a second layer would add to that, she said.
"The double masking idea is that more layers of mask in front of your [face] equals more protection," Smith said.
"There's no downside to you in double-masking on your own in public at this point, even though it's a little more cumbersome, and you're helping everyone else" reduce their risk for COVID-19, she said.
The only issue with double-masking, and perhaps the reason the CDC has yet to formally recommend it, is supplies, Smith said.
Earlier in the pandemic, healthcare facilities reported shortages of N95 masks, which are among the most effective at limiting virus transmission, and other personal protective equipment, she said.
Although these supply issues seem to have been resolved, they could return if demand for masks continues to rise, according to Smith.
Staff members at Duke University Hospital in Durham, N.C., where she is medical director of infection control, continue to wear one medical-grade mask on the job because double-masking is "cumbersome" during patient care, she said.
However, the healthcare workers there and at other hospitals across the country have the added benefit of being prioritized for the COVID-19 vaccines and regular testing for the virus, Smith said.
But the masking policy could change if the CDC modifies its guidance on face coverings based on the growing prevalence of new strains nationally, she said.
For now, the new virus strains remain "relatively rare" in the United States and shouldn't cause "much of concern" yet as state and local governments consider reopening businesses and schools, Montefiori said.
Still, the variants that have emerged, including those from England, South Africa and Brazil, include genetic mutations in the virus' "spike protein," which enables it to take hold in the body, he said.
The available vaccines essentially teach the immune system to recognize and respond to that spike protein, so any changes to it could compromise their efficacy, Montefiori said.
To date, research suggests that both the Pfizer-BioNTech and Moderna vaccines approved for use in the United States still offer protection against these new variants of COVID-19, he said, though they are less effective.
Newer vaccines from Johnson & Johnson and Novavax, which could be green-lighted in the next several weeks, are also expected to be at least somewhat less effective against the emerging variants -- specifically the one traced to South Africa -- according to Montefiore.
If the vaccines are less effective against the newer strains in general, that could increase the likelihood that COVID-19 will become "endemic," or a seasonal virus like the flu, making achieving herd immunity even more challenging, he said.
"It's no surprise this virus is mutating, the only question is how fast is it mutating," Montefiori said.
"With daily new infections going down sharply in the past few weeks, the U.S. might be approaching herd immunity, but it's still possible the new variants might be resistant to that immunity," he said.