“The delta variant is showing every day its willingness to outsmart us and to be an opportunist in areas where we have not shown a fortified response against it,” Walensky told reporters in July.
The good news, Walensky has said, is that all three coronavirus vaccines available in the United States offer strong protection against severe disease and death from covid-19, the disease caused by the virus. Preliminary data from several states over the past several months suggests that 99.5 percent of covid-19-related deaths occurred among unvaccinated people, she has said.
Here are answers to common questions about the delta variant and how to help protect yourself.
Frequently Asked Questions
What is the delta variant?
The delta variant, also known as B.1.617, was first detected last year in India, where it has been ravaging the nation and has since spread to dozens of other countries, upending plans for a return to normalcy.
Delta has several lineages with slightly different sets of mutations. One of those — B.1.617.2 — is also now the dominant coronavirus variant in the United Kingdom, where it accounts for the majority of all covid-19 cases in that nation.
The variant has spawned another variant, known as delta plus, that has been reported in Britain, India and the United States. The effect of delta plus remains to be studied thoroughly, though researchers are somewhat reassured that it has not taken a stronghold on the countries where it has been detected.
Overall, health experts describe delta as the most “fit” variant of the coronavirus. That means it probably will outcompete other variants and make more people sick from covid-19, said Monica Gandhi, an infectious-disease expert at the University of California at San Francisco. “It’s the one that is most likely to latch onto cells in a host, and it attacks that host better than the other variants, because it can replicate itself better.”
Why is the delta variant a concern?
Early research suggests the delta variant is about 50 percent more contagious than the alpha variant, which was first identified in the United Kingdom and became the predominant variant in the United States during the spring. Alpha was already about 50 percent more transmissible than the original variant of the coronavirus first identified in Wuhan, China, in late 2019.
The delta variant has changed the fight against the coronavirus as data has proven that it is highly contagious, likely to cause more severe disease and that breakthrough cases may be as transmissible as unvaccinated cases, according to an internal CDC slideshow that was leaked to The Post.
“Vaccinated people are transmitting it, and the extent is unclear, but there’s no doubt they’re transmitting it,” Anthony S. Fauci, President Biden’s chief medical adviser, said back in July. “People who are vaccinated, even when they’re asymptomatic, can transmit the virus.”
The document noted the vaccines prevent more than 90 percent of severe infections but may be less effective against milder infections.
Public Health England (PHE) found that the variant may be associated with a higher risk of hospitalization, and some early research from Scotland suggests that the risk of hospitalization with covid-19 from the delta variant is about twice the risk from the alpha variant — with unvaccinated individuals at the greatest risk.
But health experts caution that there is not yet conclusive evidence that delta causes more severe disease. Hospitals serving areas where it is surging have reported admitting more young and middle-aged covid-19 patients, but that may be because they are less likely to be vaccinated.
Delta is also causing more infections in kids.
More than 4 million children have been diagnosed with the coronavirus during the pandemic, and recent data from the American Academy of Pediatrics shows that infections in children have been steadily rising since early July.
How effective are the vaccines against the variant?
Real-world data suggests that the Pfizer-BioNTech vaccine (which has been granted full approval by the Food and Drug Administration for people 16 and older) and the Moderna and Johnson & Johnson vaccines (which are authorized for emergency use) offer strong protection against severe disease and death from the delta variant, though they appear to offer less protection against minor to moderate infections.
Such data has come not only from the United States but also from other countries.
“I think this is a really important point, because that’s our primary goal with our vaccination effort: to prevent severe disease, to prevent hospitalization, to prevent deaths,” said William Moss, a professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health.
In the case of the two-dose messenger RNA vaccines — Pfizer-BioNTech and Moderna — both shots are needed to mount a strong response against the delta variant. A study published in July in the New England Journal of Medicine found that the Pfizer-BioNTech vaccine was 36 percent effective against symptomatic disease caused by the delta variant after the first shot of the two-shot regimen, but 88 percent effective after the second shot. It supports earlier findings from PHE.
Others, such as a study in Israel, found larger declines in protection against infection. One U.S. report that has not yet gone through peer review, collecting data from Mayo Clinic Health System facilities in five states, found a drop in the Pfizer-BioNTech vaccine’s effectiveness against delta infections to 42 percent. The other mRNA vaccine, made by Moderna, was 76 percent effective.
In terms of preventing hospitalizations from delta, a PHE paper suggested that the Pfizer-BioNTech vaccine was 94 percent effective after the first shot and 96 percent effective after the second.
As for the Johnson & Johnson vaccine, one journal preprint showed that it had a diminished immune response to the delta variant in laboratory tests. Other studies, including one published in the New England Journal of Medicine, suggest that it can provide robust protection for months after vaccination. Some researchers say the Johnson & Johnson vaccine may end up showing similar results to the vaccine developed by British-Swedish firm AstraZeneca and Oxford University, which was included in the PHE studies and found to be 60 percent effective against symptomatic disease and 92 percent effective against hospitalization after both doses. The Oxford-AstraZeneca vaccine has not been approved for use in the United States.
All that said, emerging research is beginning to show a decline in vaccine effectiveness as delta surges across the United States.
Based at least partly on that data, the Biden Administration announced that it will begin offering coronavirus booster shots starting in mid-September to fully vaccinated adults who previously completed an mRNA vaccine series in an effort to combat waning immunity.
The data did show protection against hospitalization remains strong.
What else can people do to protect themselves?
Health experts say that people who are not yet vaccinated should continue to wear masks and make plans to get vaccinated as soon as they can.
Citing new evidence that vaccinated people can also spread infections, the CDC announced in July that everyone living or working in high-transmission communities should resume wearing masks in indoor public spaces, including the vaccinated. It also recommended that vaccinated people with vulnerable household members, including young children and those who are immunocompromised, wear masks in indoor public spaces.
In addition, the agency called for universal masking for teachers, staff members and students in schools, regardless of their vaccination status.
For those experiencing symptoms, health experts say testing is key to rule out potential breakthrough infections.
What about people who are immunocompromised?
Vaccination is still the top recommendation to protect against the virus, including the delta variant, although not all immunocompromised people may mount a robust response. But others will build immunity from the shots, and there appears to be no harm from getting immunized, said William Schaffner, medical director of the National Foundation for Infectious Diseases.
In addition, the FDA has authorized additional mRNA vaccine doses for people who are moderately to severely immunocompromised.
The CDC now recommends that people with certain immune system deficiencies — including those being treated for certain cancers, those who have received an organ transplant and those who have chronic medical conditions that can weaken immune responses — get a third shot of Pfizer-BioNTech or Moderna at least 28 days after completing the initial two-dose series.
There is no need to get a prescription. Those who are immunocompromised need only to attest that they have immune-system deficiencies.
Beyond vaccines, individuals with compromised immune responses should practice social distancing, wear masks and avoid crowds, particularly indoors.
“Those things continue to pertain to these highly susceptible people,” Schaffner said.
Schaffner, a professor of infectious diseases and preventive medicine at Vanderbilt University, said it’s also important for immunocompromised people to get tested if they experience symptoms, especially as the new influenza season rolls around, so they can get treated appropriately — either for flu or covid-19. In some cases, for example, antiviral medications may be used to treat influenza and monoclonal antibodies may be used to treat covid-19, which can reduce the risk of hospitalization and death when used early in the course of disease.
What about the risk to children, and how can parents protect them?
Because delta is more contagious than earlier variants, children are at somewhat greater risk of infection. Those who are 12 and older are eligible for the Pfizer-BioNTech vaccine, and federal health officials recommend that families inoculate eligible children to provide them greater protection.
Paul A. Offit, a pediatrician and the director of the Vaccine Education Center at Children’s Hospital of Philadelphia, suggests parents make sure that unvaccinated children ages 2 or older wear masks when they are in indoor public spaces, in accordance with CDC guidance.
The CDC also recommends parents make sure their unvaccinated children wash their hands often with soap and water; avoid close contact with those who are coughing, sneezing or complaining of feeling unwell; and limit interactions with people who are at high risk of developing severe disease.
How will the delta variant affect the United States?
With more than half of the U.S. population now fully vaccinated against the coronavirus, the delta variant is not expected to cause the massive death toll of the earlier outbreaks. Instead, health experts anticipate that it will cause surges in communities where vaccination rates are lower, posing the most serious risk to those who are older, sicker and unvaccinated.
Delta has led to a resurgence in infections since it became the dominant variant in July.
Nearly all coronavirus deaths in the country have happened among unvaccinated people, according to a White House briefing released earlier this month.
“We’re going to have to face it throughout the United States,” said Eric Topol, a professor of molecular medicine and executive vice president at Scripps Research.
Topol said the states that are most vulnerable are the ones that have had fewer coronavirus cases and lower vaccination rates, meaning they do not have as much natural and vaccine-induced immunity. States with higher vaccination rates, such as Connecticut, Massachusetts and Vermont, have “a delta wall,” he said.
Do symptoms from delta infections differ from infections from other variants of the coronavirus?
There is little research on this, but some people have reported symptoms such as a headache, sore throat and runny nose, without the hallmark covid-19 signs, such as a loss of taste and smell.
Will booster shots be needed?
The Biden administration announced Aug. 18 that starting the week of Sept. 20, it will begin offering booster shots — or, a third dose of the Pfizer-BioNTech or Moderna vaccine — for Americans eights months after completing their initial mRNA vaccination series.
Health officials said that currently, there is no plan for a booster for people who received the Johnson & Johnson vaccine, but it is under review.
The decision was driven, at least in part, by the recent data showing declining immunity from the vaccines to protect against less severe disease.
“Around the six-month mark in the data, you start to see increases in mild to moderate infection,” U.S. Surgeon General Vivek H. Murthy told reporters, adding that “the most important purpose of the vaccine is to keep us out of the hospital and to save our life.”
“And, fortunately, we are seeing that still holding at a high level, which is good news,” Murthy continued. “But our anticipation is that if the trajectory that we are seeing continues, that we will likely see in the future an increase in breakthrough hospitalizations and breakthrough deaths.”
The bottom line is that people need to take measures to protect themselves and their loved ones against the delta variant, experts said.
“If you haven’t had covid, you’re not vaccinated and you’re not wearing a mask, you’re basically asking for delta trouble. It’ll find you,” Topol explained.
Ben Guarino contributed to this report