The Gamma Variant’s Rise in Washington State

On top of a historic heat wave, the Pacific Northwest has been hit with a rise in COVID-19 cases caused by the Alpha, Delta, and Gamma variants. And while much of the world is focused on Delta, or B.1.617.2, government officials in Washington state are particularly wary of Gamma (P.1).

Washington state’s leading COVID-19 strain remains Alpha (B.1.1.7), first detected in the U.K. But according to recent data released by the state’s Department of Health (DOH), cases caused by Gamma reached 16.3% in mid-June — a decrease from a high of 20.6% in May. Delta cases increased by more than 10% from May to June, now making up 17.6% of infections in the state — all while Alpha cases continue to slowly dwindle.

Although the Delta variant has eclipsed Gamma cases in Washington in recent weeks, state epidemiologist Scott Lindquist, MD, MPH, has continued to express his worries about Gamma’s detrimental impact.

“Our Delta variant is not as aggressive, it’s not causing as many hospitalizations or deaths as would be predicted, but the P.1 tends to be causing more hospitalizations and deaths,” Lindquist said in a DOH briefing about the state’s June 30 reopening.

The Gamma variant was, in fact, associated with the highest number of hospitalizations and deaths in comparison to any other strains of COVID-19, including Alpha and Delta, according to the DOH report.

Notably, Gamma was detected in 17% of breakthrough infections after vaccination, making it second overall — after Alpha — in vaccine breakthroughs.

Despite these data, Lindquist assured that “all the vaccines we have in Washington state still show effectiveness for these variants,” as Washington’s DOH continues its vaccination campaign. “It’s much more of a risk to be unvaccinated in this state right now than it is any concern for the vaccine not working against these variants,” he said.

Gamma was first identified among travelers from Brazil at the beginning of January during a routine screening at an airport in Japan. When Gamma became the dominant strain of SARS-CoV-2 in Brazil not long after, both the World Health Organization and the CDC designated Gamma as a variant of concern. Now, it has been identified in at least 37 countries and 31 U.S states.

After Manaus, the capital of Brazil’s Amazonas region, was struck with a wave of COVID cases in the spring of 2020, certain studies suggested that the city may have reached herd immunity. However, the Gamma variant caused a resurgence of SARS-CoV-2 infections in Manaus in January of this year.

A study of Manaus’s COVID resurgence found that Gamma could be nearly twofold more transmissible than other variants from the same lineage. Data from Manaus indicated that “P.1-infected adult individuals are more infectious than those harboring non-P.1 viruses,” wrote Felipe Gomes Naveca, of the Leonidas and Maria Deane Institute’s Laboratory of Ecology of Communicable Diseases, and colleagues.

Gamma closely resembles the lineage of Beta (B.1.351), which was first detected in South Africa and is now a variant of concern. Because Beta and Gamma share some of the same mutations on the coronavirus spike protein, they’re both capable of overcoming the immunity that individuals may have developed after being infected by other strains.

Like Beta, Gamma contains the N501Y and K417T mutations, both of which give the virus a tighter grasp on human cells. It also carries E484K, a mutation known to help the virus evade certain types of antibodies. Vaccines, therefore, may offer less protection against the Gamma variant than others.