The Delta Variant and Unvaccinated Individuals Present Significant Challenges to Eradicating COVID-19

Since COVID-19 emerged as a global threat approximately 18 months ago, numerous coronavirus variants have circulated worldwide. The delta variant, initially identified in India in December 2020, is the latest cause for alarm. Estimated to be roughly 60% more contagious than the highly transmissible alpha variant first discovered in the U.K., delta has now reached at least 124 countries, including the United States.

During a Senate committee hearing on Tuesday, July 20, CDC Director Rochelle Walensky stated that the delta variant is now the predominant strain in the U.S., making up 83% of sequenced COVID-19 samples. In certain parts of the country, this figure is even higher.

The World Health Organization (WHO) has classified delta as a global "variant of concern" (VOC), attributing it to the devastating surge of infections that overwhelmed India. On June 9, the country reported a record-breaking daily high of over 6,000 deaths in a single day.

"This virus could prove to be one of the most challenging we've encountered so far," remarks Dr. Paul Goepfert, a professor of medicine at the University of Alabama at Birmingham and a specialist in vaccine development.

What Is the Delta Variant?

COVID-19, caused by the SARS-CoV-2 virus, originates from a single viral species. As the original, or "wild type," virus replicates, its molecular sequence, composed of nucleotides, occasionally mutates. These mutations often render the virus ineffective or weaker.

However, some mutations can enhance the virus, making it more transmissible or resistant to the immune system. Such variants are closely monitored by the WHO's Virus Evolution Working Group, which identifies and evaluates their potential global impact.

Delta is the fourth variant of concern designated by the WHO since the pandemic started. The previous three — alpha, beta, and gamma — were first detected in the United Kingdom, South Africa, and Brazil, respectively. Scientifically, delta is referred to as B.1.617.2.

According to Mehul Suthar, an assistant professor of pediatrics at Emory Vaccine Center and Yerkes National Primate Research Center, the delta variant has been classified as a VOC due to specific mutations in the spike protein.

The delta variant contains at least four mutations linked to increased transmissibility and higher infectivity, based on similarities with earlier variants exhibiting comparable changes.

What Are the Symptoms of the Delta Variant?

Symptoms of the original coronavirus typically include fever or chills, cough, shortness of breath, fatigue, muscle aches, loss of taste or smell, nausea, vomiting, or diarrhea.

The delta variant, however, seems to present differently. According to data from the UK's ZOE COVID Symptom Study app, the most commonly reported symptoms in the U.K. were headaches, sore throats, runny noses, and fever.

Blood clots have emerged as a serious complication of COVID-19. Dr. Ganesh Manudhane, a cardiologist in Mumbai, India, told Bloomberg that he has observed an unusual number and variety of blood clots in COVID-19 patients of all ages, even those without prior clotting issues. Some patients developed micro thrombi, or small clots, severe enough to cause gangrene, leading to amputations of fingers or feet. "We suspect the new variant may be responsible," he said.

It’s worth noting, however, that these findings are anecdotal and not yet supported by scientific research.

How Widespread Is Delta in the U.S.?

In nations with greater vaccine accessibility, mRNA vaccines are demonstrating their effectiveness. Currently, 48.3 percent of the U.S. population is fully vaccinated, with 55.7 percent having received at least one dose. However, vaccination rates must rise as COVID-19 cases are surging nationwide due to the delta variant.

Despite being home to the world's largest vaccine manufacturer, India faces a significant internal vaccine shortage. Only slightly over 10 percent of its population has received a single dose.

"In regions with low vaccination rates, whether states, cities, or counties, the combination of a highly transmissible variant and insufficient vaccination will lead to isolated outbreaks," Dr. Anthony Fauci, the president's chief medical adviser, told CNN on June 29. "It’s almost as if we’re heading toward two distinct Americas."

This update follows a June 22 White House COVID-19 Response Team briefing, where Fauci noted that delta variant cases had doubled in roughly two weeks. In early May, delta represented just 1.2 percent of cases, but now it accounts for over 80 percent.

In early May, the alpha variant, scientifically named B.1.1.7, was still the dominant strain in the U.S. However, Fauci cautioned that delta would soon take over. "The delta variant is now the most significant threat to our efforts to eradicate COVID-19 in the U.S.," he stated during the June 22 press briefing.

Cases are rising most notably among 12- to 20-year-olds. Goepfert suggests this could be because this age group was among the last to become eligible for vaccination.

"Initially, we prioritized vaccinating older populations, which was the right decision, and we’re seeing the positive impact with reduced hospitalizations," Goepfert explains. "However, infections are now primarily affecting younger individuals. While they are less at risk, the infection isn’t entirely harmless for them. Some experience severe illness and complications."

Do COVID Vaccines Protect Against the Delta Variant?

Goepfert notes that while it’s still early to definitively confirm, preliminary data suggests that approved COVID-19 vaccines offer protection against the delta variant.

A preprint study from the U.K. indicates that a single dose of the Pfizer vaccine offers approximately 33 percent protection against the delta variant, while two doses increase effectiveness to 88 percent.

As of now, no published data exists on the effectiveness of the Moderna or Johnson & Johnson vaccines against the delta variant. However, Fauci told Judy Woodruff on PBS News Hour on July 20 that he remains confident in the vaccines' efficacy, though breakthrough infections among vaccinated individuals are expected.

"The vaccines are highly effective at preventing infection and extremely effective at preventing severe illness, but they don’t completely eliminate the risk of infection. Clinical trials demonstrated 93 to 94 percent efficacy against symptomatic disease, not asymptomatic infection," he explained. "So, breakthrough infections are expected. The positive aspect is that vaccinated individuals who experience breakthrough infections typically have mild or no symptoms."

Should You Mask Up Indoors Again?

The CDC warns that the delta variant may evade antibodies generated from vaccination or prior infection. Additionally, monoclonal antibody treatments for COVID-19 patients might be less effective against this variant. This is concerning, as a June 14 study in the Lancet found that delta variant infections are twice as likely to result in hospitalization compared to the alpha variant.

In response to rising concerns, the L.A. County Department of Public Health reinstated an indoor mask mandate on July 15, applying to all residents regardless of vaccination status. Meanwhile, the CDC maintains its May guidelines, which exempt vaccinated individuals from mask requirements, despite widespread criticism.

Moderna and Pfizer's vaccines utilize mRNA technology, with studies showing 95 percent and 94 percent efficacy, respectively, against the original virus. Johnson & Johnson's single-dose adenovirus-based vaccine demonstrated 72 percent effectiveness against the wild-type virus.

"This pandemic is increasingly affecting the unvaccinated," stated CDC Director Walensky during a briefing. Over 99 percent of U.S. deaths are now among those unvaccinated. Accelerating vaccination efforts remains the quickest path to ending the pandemic.