Washington Gov. Jay Inslee said the state has a "long ways to go" as it marks the one-year anniversary of the first U.S. case of COVID-19 being discovered in the state of Washington.

"We were hit the first and hardest," Inslee said during a press briefing Thursday. "Our recovery for the pandemic is progressing, and we have a long ways to go and we need to continue to learn from what we have experienced."

Since that first diagnosis, Washington state has reported 296,087 confirmed and probable COVID-19 cases as well as at least 4,065 deaths from the disease.

If the state "made different decisions," there could have been as many as 8,000 more people who died, Inslee said.

On the vaccination front, Washington state is administering on average more than 16,000 doses of COVID-19 vaccines per day, with plans to open four mass-vaccination sites next week, according to the governor.

Amazon will also open a one-day pop-up clinic in Seattle on Sunday, with the aim of administering 2,000 vaccines, Inslee said.

The governor urged residents to "remain diligent" amid the vaccine rollout.

"If we deviate from that course, we will have thousands more deceased Washingtonians in the months to come and that's just a hard fact," he said.

-ABC News' Michelle Mendez contributed to this report

New COVID-19 cases and deaths reported in the United States decreased substantially in week-to-week comparisons, according to a Health and Human Services memo obtained by ABC News Thursday.

Twenty-six states are in a downward trajectory of new cases, the memo stated.

The number of new cases confirmed from Jan. 15 to 21 decreased 20.4% compared to the previous seven-day period. The number of deaths decreased 9.2% during that time.

The national test-positivity rate dropped to 10.6% from 13.1% in week-to-week comparisons.

The percentage of hospitals with more than 80% of their intensive care unit beds filled and the percentage of inpatients with COVID-19 have also decreased slightly, according to HHS.

ABC News' Josh Margolin contributed to this report.

A Texas doctor is accused of stealing a COVID-19 vaccine vial that contained nine doses, according to Harris County District Attorney Kim Ogg.

Dr. Hasan Gokal of Harris County Public Health allegedly took the vial while working at a county vaccination site on Dec. 29. He was fired and has been charged with theft by a public servant, Ogg said.

"He abused his position to place his friends and family in line in front of people who had gone through the lawful process to be there," Ogg said in a statement. "What he did was illegal and he'll be held accountable under the law."

Gokal's lawyer, Paul Doyle, told Houston ABC station KTRK in a statement that the reason he took the vial was because the doses were going to expire.

"Dr. Gokal is a dedicated public servant who ensured that COVID-19 vaccine dosages that would have otherwise expired went into the arms of people who met the criteria for receiving it," Doyle said. "Harris County would have preferred Dr. Gokal let the vaccines go to waste and are attempting to disparage this man's reputation in the process to support this policy. We look forward to our day in court to right this wrong."

Dr. Anthony Fauci, chief medical adviser to U.S. President Joe Biden, said his “best-case scenario” is getting 85% of Americans vaccinated by the end of the summer.

"If we get 70% to 85% of the country vaccinated, let’s say by the middle of the summer, I believe by the time we get to the fall, we will be approaching a degree of normality," Fauci, who is also the director of the National Institute of Allergy and Infectious Diseases, told reporters at Thursday's White House press briefing.

"If we get 75% to 80% vaccinated, we could have a degree of herd immunity to get us back to normal," Fauci added. "The concern I have is people who have vaccine hesitancy who don't want to get vaccinated. We need to do a lot of good outreach."

Fauci said he believes Biden’s goal of 100 million vaccinations in his first 100 days as president "is quite a reasonable goal."

California's top epidemiologist has recommended pausing the administration of COVID-19 vaccines from Moderna's lot 041L20A due to "possible allergic reactions" that are under investigation.

"A higher-than-usual number of possible allergic reactions were reported with a specific lot of Moderna vaccine administered at one community vaccination clinic," Dr. Erica Pan, state epidemiologist for the California Department of Public Health, said in a statement late Sunday night. "Fewer than 10 individuals required medical attention over the span of 24 hours. Out of an extreme abundance of caution and also recognizing the extremely limited supply of vaccine, we are recommending that providers use other available vaccine inventory and pause the administration of vaccines from Moderna Lot 041L20A until the investigation by the CDC, FDA, Moderna and the state is complete."

The California Department of Health said all of the affected individuals appeared to be experiencing "a possible severe allergic reaction during the standard observation period," which the U.S. Centers for Disease Control and Prevention says some people have experienced when receiving a COVID-19 vaccine.

More than 330,000 doses from that specific lot have been distributed to 287 providers across the state, with the shipments arriving between Jan. 5 and 12, according to the California Department of Public Health, which said it has not been notified of any other cluster or individual events related to this lot.

When asked for comment, a spokesperson for Moderna told ABC News: "Moderna acknowledges receiving a report from the California Department of Public Health (CDPH) that a number of individuals at one vaccination center in San Diego were treated for possible allergic reactions after vaccination from one lot of Moderna’s COVID-19 Vaccine. The company is fully cooperating with CDPH in investigating these reported adverse events. Consistent with the statement from CDPH, at this point Moderna is unaware of comparable adverse events from other vaccination centers which may have administered vaccines from the same lot."

ABC News' Sony Salzman contributed to this report.