COVID-19 updates: Classes in Chicago canceled for 4th day

Florida allowed up to a million COVID-19 rapid test kits to expire last month, according to Florida Division of Emergency Management Director Kevin Guthrie.

Guthrie admitted during a press conference Thursday that the stockpile of unused tests, manufactured by Abbott Laboratories, sat idle in a Florida warehouse amid a lack of demand for them.

"We had between 800,000 and 1 million test kits -- Abbott rapid test kits -- in our warehouse that did expire," Guthrie told reporters. "We tried to give them out prior to that, but there was not a demand for it."

The tests expired between Dec. 26 and Dec. 30, after being granted a three-month extension, according to Guthrie. Meanwhile, the country has been grappling with a winter surge of COVID-19 infections, fueled in part by the highly contagious omicron variant and holiday gatherings, that has sparked an increased demand for tests, leading to shortages and long lines across the nation.

Florida Agriculture Commissioner Nikki Fried, a Democratic candidate for governor, has accused Florida Gov. Ron DeSantis and the Florida Department of Health of stockpiling tests amid hourslong lines at testing sites in some parts of the Sunshine State.

The number of global cases of COVID-19 crossed 300 million on Thursday night, according to data compiled by Johns Hopkins University.

The U.S. continues to have the most cases in the world -- as it has all pandemic -- with over 58 million cases. India (35 million), Brazil (22 million), the U.K. (14 million) and France (11 million) round out the top 5 countries by total cases.

Global cases crossed 200 million on Aug. 4, 2021, and 100 million on Jan. 26, 2021, according to JHU.

With many people now experiencing second bouts of the virus, it's unclear how many total people have been infected globally.

Chicago Public Schools, the nation's third largest school district, canceled instruction on Friday for the third day in a row amid an impasse over in-person learning.

Classes were first canceled Wednesday, and then again on Thursday, after a majority of the Chicago Teachers Union's membership voted this week in favor of remote learning during a surge in COVID-19 cases.

The district said Thursday evening that all classes will be canceled on Friday, though some schools may be able to offer in-person activities for students.

"Our schools are the best, safest place for students to be during this pandemic, and we are working tirelessly to get everyone back in class every day," Pedro Martinez, head of the school district, said in a letter to families, noting that they are continuing to work with the union "to resolve this situation."

The teacher's union is calling for more robust school COVID-19 testing and contact tracing.

Johnson & Johnson's single-shot COVID-19 vaccine offers lower initial efficacy compared to Pfizer's and Moderna's, but protection against breakthrough infection remains more stable over time, according to a new study sponsored by the pharmaceutical company.

The study found that the J&J vaccine was 74% effective against breakthrough infection in the weeks following the shot. This level of protection held steady over the next three months and started waning after the fourth month.

The Pfizer and Moderna vaccines, meanwhile, were 88% and 92% effective, respectively, against breakthrough infection in the weeks following the second dose, the study found. This level of protection started waning after the second month, falling progressively over six months.

Protection against severe illness remained more stable over time for all three vaccines.

The analysis, which has not been peer-reviewed, looked at data from 168 million people between Jan. 1 and Sept. 7 of last year. It covers a period of alpha and delta variant dominance, but the results could change now that the omicron variant is also present. 

The data supports current guidance from the Centers for Disease Control and Prevention for booster shots after two months for the J&J vaccine to bring initial efficacy higher, and booster shots for Pfizer and Moderna vaccines after five and six months, respectively, to boost efficacy after a period of waning. 

-ABC News' Sony Salzman