Grocery store and meatpacking workers said they still feel just as vulnerable to contracting COVID-19 now as they did at any point during the pandemic. In an organized call, the United Food Commercial Workers union called for hazard pay and that food service workers be prioritized for the vaccine.

At least 137 grocery workers and 132 meatpacking workers have died from COVID-19, according to the call.

Guidelines from the Centers for Disease Control and Prevention say that front-line essential workers, like grocery store employees, should be prioritized for the vaccine. But not every state has done so and union officials said their workers still can't get the vaccine even when it's being offered at the pharmacy in the store where they work every day.

"What is inexplicable, given the threats and the risks that these essential workers face and the fact that a new report, it shows only 13 states currently prioritize access for food workers, which puts our food supply at risk,” said UFCW President Marc Perrone.

ABC News’ Stephanie Ebbs contributed to this report.

The Biden administration will start sending vaccines directly to community health centers across the country as early as next week, White House COVID-19 Response Coordinator Jeff Zients said at a press briefing with Health Equity Task Force Chair Dr. Marcella Nunez-Smith.

The administration's goal is to reach 250 community health centers and at least one in every state, Nunez-Smith said.

The administration plans to issue 1 million doses during this initial phase: 500,000 first shots and 500,000 second vaccine shots.

FEMA mobile units will also be going directly to these hardest-hit communities, Zients said. Earlier this week, FEMA announced that it had finalized a contract for 30 mobile vaccination units expected to begin next week.

ABC News’ Matthew Vann contributed to this report.

A variant found last week in Bristol, England, has now been discovered in Manchester.

The Manchester City Council announced Monday night that four cases were found in two unconnected households. Testing is underway in the Manchester area to track the variant.

Separately, a new mutation was found in Liverpool.

Public Health England said it has a high degree of confidence that the vaccines will work against variants.

ABC News’ Zoe Magee contributed to this report.

As some students from Nashville to North Carolina return to the classroom, National Education Association President Becky Pringle says the in-person learning standards set by the Centers for Disease Control and Prevention "still aren’t being met."

"Most schools, especially those attended by Black, brown, indigenous, and poor white students have severely outdated ventilation systems and no testing or tracing programs to speak of," Pringle said in a statement. "It’s time to fund proven mitigation strategies -- and it’s far past time for every governor to prioritize educator vaccinations."

In Chicago, 25,000 public school teachers will begin voting Tuesday night on a proposal for returning to classrooms, ABC Chicago station WLS reported.

ABC News’ Sophie Tatum contributed to this report.

An international team of World Health Organization experts investigating the origins of the coronavirus pandemic said Tuesday it's "extremely unlikely" that the virus was leaked from a laboratory in the Chinese city of Wuhan.

The Wuhan Institute of Virology, which is affiliated with the government-run Chinese Academy of Sciences, has collected extensive virus samples, sparking speculations that it may have caused the original outbreak by leaking the novel coronavirus into the surrounding community. The institute has strongly rejected that possibility.

"The findings suggest that the laboratory incident hypothesis is extremely unlikely to explain the introduction of the virus into the human population," WHO food safety and animal diseases expert Peter Ben Embarek said at a joint press conference with Chinese counterparts on Tuesday. "Therefore, [it] is not in the hypotheses that we will suggest for future studies."

The WHO team, which includes experts from 10 countries, is considering several possible scenarios for how the disease was transmitted to humans, leading to a pandemic that has claimed the lives of more than 2.3 million people worldwide. Embarek said it's more likely that the virus jumped to humans from an animal.

"Our initial findings suggest that the introduction through an intermediary host species is the most likely pathway and one that will require more studies and more specific targeted research," he said.

Transmission through the trade of frozen products was also likely, Embarek added.

As part of their investigation, the WHO team has visited key locations in Wuhan, where the first cases of COVID-19 were detected in December 2019.

A cluster of initial cases has been linked to a now-closed wet market in Wuhan. But Liang Wannian, the lead Chinese envoy who is working on the probe, said the market may not be the first location of the outbreak since transmission was also happening in other areas of the city at the time.

A review of mortality data, antibody tests of blood in blood banks in Wuhan and genome sequences showed there was "no indication of the transmission of the Sars-Cov-2 in the population" prior to December 2019, according to Liang.

There was also no evidence of "large outbreaks" in Wuhan or elsewhere before December 2019, according to Embarek.

ABC News' Karson Yiu contributed to this report.