The US and the delta variant: A new chapter to the pandemic

The United States kicked off the month of August with great news: On Monday, the White House announced that 70% of American adults had received at least one shot of a COVID-19 vaccine. 

Data published by the US Centers for Disease Control and Prevention (CDC) also indicates that the pace of COVID vaccinations in the US has risen steadily over the past three weeks — a trend not seen in months. That shift includes southern states known for low vaccination rates as a direct result of vaccine hesitancy.

But as vaccination increases, so, too, does the pace of infection and hospitalization. Driving the latest wave of illness is the highly contagious delta variant, which according to the CDC, accounts for more than 93% of all new COVID-19 cases in the country.

Reaching herd immunity proves difficult despite vaccinations

Getting at least 70% of the population vaccinated was a pledge that President Biden made upon taking the office. He said it was a crucial step toward reaching so-called herd immunity — the point at which enough members of a community have developed antibodies against a specific disease that the larger whole becomes immune to it. 

But now, despite reaching that planned threshold, health experts doubt the United States will be able to return to normal any time soon.

With the delta variant spreading much faster than the original virus, a higher proportion of the population needs to be vaccinated before the the spread of the virus can be brought under control.

"When we recalculate the percent of the population that we will need to have vaccinated in order to substantially reduce the amount of circulating virus, the number is going to be higher than 70%. It's probably going to be in the 85% or 90% rate, to get what is called herd immunity," says Timothy Murphy, a senior professor of infectious disease from the Jacobs School of Medicine at the University of Buffalo.

Unvaccinated communities fall prey to new outbreaks

One of the reasons for the rise in infections is the disparity between vaccination rates in different communities.

"There is extreme local variation in vaccination rates, so outbreaks will continue to happen," says Rachael Piltch-Loeb, a researcher at the School of Global Public Health at New York University. "In the face of new variants, the goal should be as many individuals vaccinated as possible in every community."

Health officials in the United States have referred to the new outbreaks as a pandemic of the unvaccinated, underscoring the fact that areas with lower than average vaccination rates have seen the most spread of infection.

The vast majority of hospitalizations and deaths at the moment are among those who have refused to be vaccinated. "Currently we understand that the overwhelming majority of severe infection is in those individuals who are unvaccinated," Piltch-Loeb says. 

A retreat in the pandemic

The spread of the delta variant does not exclusively concern the unvaccinated population, however. An outbreak in Massachusetts, a state with a high vaccination rate, revealed the threat posed by the delta variant even for the vaccinated.

The CDC's recent investigation into a coronavirus outbreak in Provincetown, Massachusetts, found that three-quarters of infections occurred in fully vaccinated people.

The organization's data also suggested that inoculated individuals could potentially spread the virus just as much as an unvaccinated person.

The realization that the delta variant can infect vaccinated individuals is changing the way the US is handling the pandemic, with officials taking a step back and asking millions of citizens to resume wearing masks while reinstating other previous COVID-19 restrictions. 

Last week, the CDC changed its guidelines to recommend everyone, regardless of vaccination status, wear masks in COVID-19 hot spots. The states of Louisiana and Nevada ordered nearly everyone, vaccinated or not, to wear masks again in all indoor public settings, including schools and colleges.

Other cities and states likewise moved to reinstate precautions to counter a looming crisis. New York City, for instance, will require proof of vaccination for indoor dining and some companies across the country have begun to mandate COVID-19 vaccines for their employees. 

Vaccination remains the only way out 

The policy changes may have also helped drive vaccination in the US: "As people feel the impact of these public health measures, they may also be seeing friends and family infected with the virus. The combination of policy changes and perception changes may be driving some to be vaccinated," says Rachael Piltch-Loeb.

But there is a concern that the return of COVID restrictions, coupled with an intense focus on infections in vaccinated people — dubbed "breakthrough cases" — might yet again discourage some people from getting the shot.

"The message people may get if we do too much focusing on these breakthrough cases is that, hey, it's not worth getting a vaccine. It's not going to protect me, anyway," says Timothy Murphy. "But let me remind you, the breakthrough cases are well below one percent of all the new infections."

Murphy is referring to a recent state-by-state study that shows only 0.1% to 0.9% of fully vaccinated people experienced a breakthrough infection.

"Vaccinated folks do not end up in the hospital, in an ICU, or the morgue," says Murphy. "I think that once our communities get to a point where we have a relatively large percentage of people vaccinated, then the likelihood of having a shutdown again is pretty low."