Could delta change the trajectory of COVID-19 in the US?
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After weeks of declining case counts, followed by a plateau, the United States is seeing an increase in COVID-19 in many parts of the country again, a CDC official warned this week.
According to Jay C. Butler, MD, the CDC’s deputy director for infectious diseases, cases are up from 20,000 a day to around 50,000 per day, accompanied by increases in hospitalizations and testing.
Source: National Institute of Allergy and Infectious Diseases.
Test positivity is up to 3.5%, although COVID-19-related deaths are not increasing and are holding steady at less than 200 per day, Butler said during a media briefing hosted by the Infectious Diseases Society of America.
The increases are due, in part, to the delta variant becoming the dominant SARS-CoV-2 virus in the country. The variant, which was first identified in India, is estimated to be the cause of more than 51% of new COVID-19 cases, noted Infectious Disease News Editorial Board Member Gitanjali Pai, MD, AAHIVS, FIDSA.
“Current estimates are suggestive of aggressive spread of the delta variant in several parts of the country,” Pai, who is the chief medical officer for the Oklahoma State Department of Health and an infectious disease physician at Memorial Hospital and Physicians' Clinic in Stilwell, Oklahoma, told Healio.
Butler said that although the delta variant is more transmissible, currently available COVID-19 vaccines remain effective against it.
“Any variant that emerges concerns us in terms of [changing] the severity of illness, [affecting] treatment options and — most important for those of us worried about prevention of COIVD-19 — if they impact the effectiveness of the vaccine,” Butler said.
As of July 13, more than 56% of eligible Americans are fully vaccinated, and two-thirds have received at least one dose, according to CDC tracking. Although there have been rare breakthrough infections, “we’re not seeing evidence of waning immunity in people who were vaccinated back in January,” Butler said.
Infectious Diseases News Editorial Board Member Jeanne M. Marrazzo, MD, MPH, FACP, FIDSA, director of the division of infectious diseases and endowed chair in infectious diseases at the University of Alabama at Birmingham School of Medicine, said the U.S. should be worried about the delta variant’s potential to change the trajectory of the COVID-19 pandemic in the U.S.
“The impressive increase in concerning outcomes — not just numbers of cases, but also hospitalizations, largely among the unvaccinated — directly correlates with delta becoming the predominant strain in the U.S.,” she told Healio. “Increased transmission efficiency will support more rapid spread among unvaccinated people and more rapid acquisition among the small minority of vaccinated people — 5% to 10% — in whom vaccine won’t be effective.”
Marrazzo said areas with “less than optimal” vaccination coverage should be watched closely for transmission.
“The concern with delta is primarily that it transmits more effectively, and we have large pockets of unvaccinated people in the country,” Abraar Karan, MD, MPH, DTM&H, an internal medicine physician at Brigham and Women's Hospital and Harvard Medical School, told Healio.
“Given that many feel like the pandemic is ‘over,’ I am concerned that we are going to reach a plateau for vaccinations lower than where it should be,” Karan said.
Although the authorized vaccines are somewhat less effective at preventing symptomatic illness from delta, they are very effective in preventing serious death and illness, Pai noted. In the case of two-dose vaccines, receiving both shots offers substantially better protection against delta compared with partial vaccination, Pai said.
“This is a sincere plea to all health care providers to encourage patients, friends, family and loved ones to get vaccinated,” she said. “As health care providers, we must continue to do our part as credible and trusted members of our communities. Vaccinating as many people as possible, as quickly as possible, and spreading the word will help us get to the other side of this pandemic sooner."
How long vaccine immunity or immunity from natural infection will provide protection from all strains, including delta, is unclear.
“Only time will tell,” Karan said.
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