The Delta variant of Covid 19 has now been detected in all 50 states and Washington, DC, according to the latest tally from CNN. The last state to report the variant is South Dakota, which confirmed its first case on Tuesday. With the more transmissible variant spreading, this puts even more pressure on local and state officials to vaccinate more people. Dr. Anthony Fauci said Tuesday he’s “very concerned about” the stark disparity between places with low and high vaccination rates. This unfortunately could lead to there soon being “two Americas” – one where most people are vaccinated and another where low vaccination rates could lead to case spikes. “When you have such a low level of vaccination superimposed upon a variant that has a high degree of efficiency of spread, what you are going to see among undervaccinated regions – be that states, cities or counties – you’re going to see these individual types of blips,” he said. “It’s almost like it’s going to be two Americas.” Young people – age 18 to 24 – are still a group that officials are trying to get vaccinated. The proportion of young people hospitalized is increasing, according to Dr. Rochelle Walensky, Centers for Disease Control and Prevention director. Since May, people ages 12 to 29 have accounted for about a third of hospitalizations – a greater proportion than in the past, Walensky said. CDC data shows, however, that vaccination coverage among young adults is improving. Over the past two weeks, the 18-24 age group made up 12.6% of those becoming fully vaccinated, the CDC said. But spikes in coronavirus cases are “entirely avoidable, entirely preventable” with vaccination, said Fauci, who heads the National Institute of Allergy and Infectious Diseases. Fauci’s remarks come as the Delta variant, which is more contagious and aggressive, has reached nearly every state and accounted for 26.1% of US Covid-19 cases as of Tuesday, according to the CDC. “I’m concerned about the Delta variant,” US Surgeon General Dr. Vivek Murthy told CNN on Wednesday. “And I am worried that what we are seeing in terms of a plateauing of cases nationally but also an increase in cases in many small sections of the United States, that that is, in fact, being driven by the Delta variant.” There is still a lot of virus circulating in the US, and close to 300 people – “just far too many” – are still dying daily from the coronavirus, Murthy said, citing data from recent weeks. “This is not over, and the virus wins when we let our guard down, when we take our eye off the ball,” he said. “We’ve seen many times that it’s fooled us in the past. We’ve got to stay vigilant, got to get vaccinated, we’ve got to talk to other people about getting vaccinated.” Indeed, the rise and spread of more transmissible coronavirus variants are changing the equation for achieving herd immunity – the point at which enough people are protected against a virus to suppress its spread – a coronavirus specialist told CNN on Tuesday. “Every time a virus gets better at transmitting, the number of people that have to be vaccinated to reach herd immunity increases,” said Andrew Pekosz, a professor of immunology at Johns Hopkins Bloomberg School of Public Health who is studying the coronavirus. “Certainly, we are not out of the woods yet because we haven’t had a vaccination rate where we get those herd immunity effects.” Places with low vaccination rates are especially vulnerable to the Delta variant, experts have said. In Mississippi, where just 29.7% of the population is fully vaccinated, unvaccinated people have accounted for more than 90% of Covid-19 cases and deaths in the past month, said Dr. Thomas Dobbs, the state health officer for the Mississippi Department of Public Health. Mississippi joins Alabama, Arkansas, Wyoming, and Louisiana in having less than 35% of residents fully vaccinated. Mask guidance stays the same in most places Even as the Delta variant spreads, most mask guidance and policies don’t appear poised to change. “For now, the CDC recommendations stand that if in fact you are vaccinated – fully vaccinated – you are protected, and you do not need to wear a mask outdoors or indoors,” Fauci said. Policies around masks on planes and public transport aren’t expected to change soon, Walensky said Wednesday on ABC’s “Good Morning America.” “Vaccinated people can take off their masks and celebrate July Fourth and feel safe in doing so, see each other smile again,” she added. “And then we’re really going to have to continue the hard work that we are doing to get people vaccinated and for those who are not to continue to protect them with mask wearing and distancing because of this Delta variant.” Children under 12 – who aren’t yet eligible for coronavirus vaccines – should continue to wear masks indoors until the Delta variant is under control in the US, Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, told CNN on Wednesday. Local differences in where the variant has spread means parents need to fully understand the risk in their area, he added. “A lot of it has to do with where you are,” Hotez said. “If you’re in the Northeast, where transmission is really low, then your kids are a lot safer than in parts of the south-central US right now, where the epidemic is really taking off, that one-two punch of the Delta variant and low vaccination rates.” Regardless of age or vaccination status, Los Angeles County has brought back its voluntary guidance to wear masks until health officials can “better understand how and to who the Delta variant is spreading,” the county’s department of public health said. And while nearly all the staff at Johns Hopkins’ public health school in Baltimore are vaccinated against Covid-19, they are still wearing masks to work, Pekosz told CNN. “We still have a masking policy here, particularly in group situations,” he said. “This pandemic isn’t over yet.” Los Angeles County appears to be the only county so far to recommend wearing masks in response to the spread of the Delta variant, the National Association of County and City Health Officials told CNN on Tuesday. But health officials are continuing to monitor the spread of the variant in the US, said Lori Tremmel Freeman, the group’s chief executive officer. Nationally, the number of people practicing safety measures, such as social distancing and masking, continues to decrease, even as 84% of Americans have heard of the Delta variant, a poll published Tuesday by Axios-Ipsos showed. The poll, conducted Friday through Monday, comprised of a nationally representative sample of 1,106 adults. Meantime, most adults who plan to get the Covid-19 vaccine have already done so, another poll shows. A Kaiser Family Foundation report released Wednesday shows 65% of adults polled have received at least one dose of the vaccine, up from 62% in May. Only 3% of those who haven’t been vaccinated said they plan to do so as soon as they can. About 14% said they will definitely not get vaccinated. In the long term, the cost of the pandemic is not just lives lost but also the mental health and well-being of people across the country, Murthy told CNN on Wednesday. “We have a long way to go to recover from this pandemic,” he said. “We can only do it together, but it starts with us getting vaccinated.” Covid-19 cases among children are dropping While children under 12 aren’t yet eligible to receive a Covid-19 vaccine, but there is some good news about declining cases. More than 8,400 new cases of Covid-19 were reported in children last week, according to the American Academy of Pediatrics’ weekly report, the lowest weekly number of cases since May 2020. Children represented about 10% of reported Covid-19 cases last week. More than 4.03 million children have tested positive for Covid-19 since the start of the pandemic. The decline in cases among children comes as the new report from the Kaiser Family Foundation indicates Covid-19 vaccination rates among children ages 12 to 17 years are rising. About 34% of parents said their eligible children have received at least one Covid-19 vaccine dose, up from 24% in May. About 8% said they plan to get their 12- to 17-year-old children vaccinated right away. Data for vaccine efficacy in children under 12 may be analyzed “in the fall/winter timeframe,” according to Dr. Peter Marks, director of the US Food and Drug Administration’s Center for Biologics Evaluation and Research. “It makes sense that it’s going to take a little longer there, because there had to be dose de-escalation – lower doses used, essentially dose de-escalation – and as well as we want to see longer follow-up data to make sure that we have the kind of safety in that population,” Marks said. Vaccines protect against Delta variant, experts say As variants spread, health experts are urging people to get fully vaccinated so they can have maximum protection. Two weeks after the second dose, the Pfizer/BioNTech vaccine is 88% effective against symptomatic infections caused by the Delta variant, Fauci has said. Those who received only one dose have less protection. Moderna’s vaccine was found in lab experiments to work against new variants including the Delta strain, the company said Tuesday. Serum samples from people who received two shots of the Moderna vaccine showed neutralizing activity against the variants, Moderna said in a pre-print study that hasn’t yet been peer-reviewed. As for the Johnson & Johnson Covid-19 vaccine, it’s “highly likely” it can protect against the Delta variant, though it hasn’t been proven through research yet, Fauci said. Two doses of the AstraZeneca Covid-19 vaccine, which uses the same platform as the Johnson & Johnson vaccine, are about 88% effective against the Delta variant, and “you can make the reasonable assumption” the Johnson & Johnson vaccine will be “just as good,” Fauci said. As of Tuesday, 46.4% of the US population was fully vaccinated, CDC data showed. Sixteen states have fully vaccinated more than half of their population. And 16 states have reached President Joe Biden’s goal to vaccinate 70% of adults with at least one dose by July 4.