The highly contagious delta variant is now the most dominant strain in Washington.

The delta variant lagged in Washington as it surged across the nation. That has changed in recent weeks, as it now accounts for the largest share of coronavirus cases in the state.

According to the state Department of Health’s (DOH) latest sequencing and variants report, delta makes up 57.5% of cases that have been genotyped, a jump from the previous report that pegged delta at 27.5%.

As delta has taken hold, those being infected are predominantly unvaccinated, Dr. Scott Lindquist, the acting chief science officer and state epidemiologist, said during a Friday news briefing.

“Let’s be honest, the majority of these are in people that are not vaccinated,” Lindquist said. “I’m very concerned about areas of the state that have lower vaccination rates, and the variant they get is going to be more infectious.”

The rise of the variant help drive King County’s top public health official to recommend residents ages 5 and up — regardless of vaccination status — wear masks again in public indoor settings.

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The guidance on Friday comes as the county is experiencing a rise in COVID-19 cases and hospitalizations related to the disease. The delta variant accounts for 56% of positive cases sequenced in King County.

King County’s top health official recommends masks in public indoor spaces — regardless of vaccination status

News of delta’s dominance in Washington comes as new questions about the one-dose Johnson & Johnson vaccine are again being raised.

A new study led by New York University’s Grossman School of Medicine found the vaccine isn’t nearly as effective as two-dose mRNA vaccines against the lambda and delta variants.

The Johnson & Johnson vaccine makes up about 4% of total doses given in Washington, according to DOH. Nationally, the one-shot vaccine accounts for around 8% of fully vaccinated people.

Lindquist said there are no signs Johnson & Johnson is performing more poorly than the Pfizer or Moderna vaccines against the delta variant. The state’s data shows breakthrough cases — when someone who is fully vaccinated gets an infection — is in proportion to the amount of each vaccine administered in Washington.

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According to DOH’s most recent report, there have been 3,446 breakthrough cases between Jan. 17 and July 17 in Washington.

State health officials are in a wait-and-see mode when it comes to next steps, such as a booster shot.

“At this time, there are no new recommendations. We are watching the new data closely and will be looking to our federal partners for ongoing guidance,” DOH spokesperson Shelby Anderson wrote in an email.

The study’s findings add to evidence that the 13 million people inoculated with the Johnson & Johnson vaccine in the country may need to receive a second dose — ideally, of one of the mRNA vaccines made by Pfizer-BioNTech or Moderna, the authors of the study said.

The new study has not yet been peer-reviewed nor published in a scientific journal, and it relied on laboratory experiments. But it is consistent with observations that a single dose of the AstraZeneca vaccine — which has a similar architecture to the Johnson & Johnson vaccine — shows only about 33% efficacy against symptomatic disease caused by the delta variant.

“The message that we wanted to give was not that people shouldn’t get the J&J vaccine, but we hope that in the future, it will be boosted with either another dose of J&J or a boost with Pfizer or Moderna,” Nathaniel Landau, a virologist at NYU, told The New York Times.

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The findings are different from a study done by Johnson & Johnson earlier this month that showed a single dose of its vaccine is still effective against delta variants for as long as eight months.

In King County, about 6% of prime doses (first doses of Pfizer and Moderna and the one-shot given of the Johnson & Johnson vaccine) have been Johnson & Johnson, according to Public Health – Seattle & King County.

Advice from the public health agency for Johnson & Johnson vaccinated people mirrors the state’s. County health officials are guided by the Food and Drug Administration and the federal Center for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP), according to Public Health spokesperson Kate Cole.

“It is possible that a booster dose may be recommended in the future, but based on their current assessment of available data, no booster doses are recommended at this time,” she said.

The Johnson & Johnson vaccine has been hounded by reports showing side effects such as blood clots and a neurological syndrome. The vaccine’s image was also hammered after it was revealed earlier this year that a manufacturing plant in Baltimore had problems with contamination.

Information from The New York Times was included in this story.