CHARLESTON, W.Va. (AP) — West Virginia will begin offering some fully vaccinated people free tests to measure antibody levels against the coronavirus, a move to study whether some elderly and immunocompromised individuals should receive a third booster shot.

State officials said they are following the lead of Israel, which announced Thursday that the country would offer a third COVID-19 booster shot for fully vaccinated people over the age of 60. West Virginia officials said the state will offer antibody testing for residents age 60 and over, particularly those living in nursing homes, who received their final vaccine dose at least six months ago.

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If the results show their antibody levels are low, a booster shot may be recommended to shore up the body’s protection against the virus. The move comes as the more contagious delta variant takes hold in the United States, leading to the return of mask mandates in some parts of the country.

Republican Gov. Jim Justice said he would not reinstate an indoor mask mandate at this time. Instead, he pledged to hold more coronavirus news briefings every week and directed his pandemic response task force to review the state’s supply of personal protective equipment and hospital capacity.

“I feel that the enemy is coming, and the enemy is this delta variant,” Justice said at a news conference.

The state recorded its 100th confirmed case of the delta variant on Thursday. Hospitalizations for COVID-19 have doubled since the start of the month, up to 133 people.

Israel, a global leader in vaccinating its citizens, has become the first country to offer a third dose of a Western vaccine to its citizens on a wide scale. West Virginia’s coronavirus czar, Dr. Clay Marsh, said the state aims to mimic Israel’s strategy and gather data on antibody levels for older and immunocompromised individuals. The data would be shared with the federal government to help officials study whether some Americans could use a third dose.

Research from multiple countries shows the Pfizer shot and other widely used COVID-19 vaccines offer strong protection against the highly contagious delta variant, which is spreading rapidly around the world and now accounts for most new U.S. infections.

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But antibodies naturally wane over time, so studies also are underway to tell if and when boosters might be needed. Pfizer has said it soon plans to seek U.S. authorization for a third dose of its COVID-19 vaccine.

Justice, who is 70, said he would have his blood drawn for an antibody test. He received his first dose of the Pfizer-BioNTech vaccine on Dec. 14, 2020, becoming one of the first public officials to receive a shot at the start of the vaccine rollout.

West Virginia lags behind five bordering states in total vaccine doses administered per 100,000 people, according to data from the Centers for Disease Control and Prevention. The state has given at least a first dose to 59% of its residents, and 49% are fully vaccinated.

James Hoyer, a retired major general leading the pandemic taskforce, said high vaccination rates among residents age 50 and over have stemmed deaths and hospitalizations, which peaked at over 800 patients in early January.

But he noted the pandemic is increasingly affecting younger people, and only 42% of people age 12 to 17 have received at least one dose. Among 18- to 29-year-olds, 47.5% have received a dose.

“We’ve got to quit paying attention to the … misinformation that’s out there, and we’ve got to get our fellow West Virginians vaccinated,” Hoyer said. “We still have a fight ahead of us.”

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