Maryland Gov. Larry Hogan, who is fully vaccinated and received a booster vaccine, has tested positive for the coronavirus, he announced on social media Monday.

Hogan received his first two doses of the Moderna vaccine in January and February, then said in August that he had received a third dose.

Hogan initially tested positive on a routine rapid test, a result that was confirmed Monday night from a more sensitive polymerase chain reaction, or PCR, test, the governor said.

Hogan said on Twitter on Monday morning that he was “feeling fine at the moment,” but later posted that he had “some cold-like symptoms.”

The Republican governor, 65, gets tested roughly weekly, plus whenever he returns from a trip, according to his office. His last negative PCR test was Thursday.

Post-vaccination infections, or “breakthrough” cases, are possible, even in individuals who have received a booster shot. Health experts say that vaccination is not 100% effective against infection, though it mostly will prevent serious illness, hospitalization and death.

Beth Blauer, data lead for the Johns Hopkins Coronavirus Resource Center, said the governor’s case underscores the importance of testing to identify cases and slow the spread of the virus.

“Governor Hogan did the right things. He got tested, and he was protected by being vaccinated and boosted,” she said. “Hopefully he continues to have a mild case and was able to limit his exposure to other people.”

But for many Marylanders, access to testing has become increasingly difficult. Whereas health departments and clinics once had many hours of testing available throughout the week and at nearby locations, testing has been scaled back dramatically

in recent months.

At the State Center testing and vaccination site in Baltimore, people waited in line for two hours Monday to get their noses swabbed. And at-home rapid test kits are flying off pharmacy shelves across the region.

“The larger question here is about testing access,” Blauer said. “Testing is getting harder to find, and more expensive because of limited supply of rapid tests. So who gets access to regular testing like the governor so they can continue to do the responsible mitigation necessary to keep their community safe?”

Dr. David Marcozzi, COVID-19 incident commander for the University of Maryland Medical System, praised Hogan for following his own advice to get vaccinated and boosted.

“It’s important to recognize that vaccines were intended to save our lives. They were not intended to decrease transmission, although they do,” Marcozzi said. “There is potential for people to be positive but not necessarily to have illness and need hospitalization.”

He added: “The governor came out and said to get two doses and a booster shot. Likely everyone needs three doses.”

Marcozzi said that with people without symptoms testing positive and able to transmit the virus, it’s important for people to continue to wear masks.

Hogan is a cancer survivor, having been treated successfully for non-Hodgkin lymphoma. He was diagnosed in June 2015, just a few months into his first term. Hogan reported still being “100% cancer-free” in 2020.

Having a history of cancer may increase one’s risk of serious illness from the coronavirus, according to the National Cancer Institute at the National Institutes of Health. People with a history of cancer are encouraged to talk to their physicians about their risks.

The governor’s diagnosis comes as the coronavirus — both the delta variant and the newer omicron variant — appear to be spreading rapidly across the United States.

Marylanders have been largely in the dark about how the surge is affecting the state after a cyberattack forced the state health department to take its servers offline earlier this month.

Monday, the agency reported new case data for the first time in more than two weeks — 28,500 Maryland residents have tested positive for COVID since the last report Dec. 3.

During the outage, the state had been reporting only vaccination statistics and hospitalizations.

The number of patients being treated for the coronavirus in hospitals has more than doubled over the past month, reaching 1,345 Monday.

It wasn’t immediately clear when or where the governor may have contracted the virus, though he has attended numerous public events recently.

On Sunday, Hogan appeared in person and mask-free for an interview on Fox News. He said that while he was concerned about the rising number of hospitalizations, he was “not anticipating any lockdowns at all.” Though Hogan frequently attends football games, he was not at M&T Bank Stadium on Sunday evening for the Ravens’ 31-30 loss to the Green Bay Packers.

On Saturday, Hogan donned a mask as he hosted participants in the Mentoring Male Teens in the Hood program at the State House in Annapolis.

On Friday, Hogan wore a mask as he attended the swearing-in ceremony of the state’s new treasurer, Dereck Davis, in the House of Delegates chamber in the State House.

Earlier last week, Hogan traveled to Palm Beach, Florida, for a Republican Governors Association event.

Hogan has been working at home at Government House in Annapolis, as contract tracing efforts got started Monday morning.

Close contacts of the governor, including key staff, have been getting tested and isolated. The entire governor’s staff has been encouraged to get tested. The office has switched to online meetings.

The coronavirus ran through the governor’s office in late August, with three members of his staff testing positive. The governor’s office said all were vaccinated and experienced mild symptoms.

That outbreak led officials at the Maryland Association of Counties to send a bulletin to thousands of members who attended a conference in Ocean City alongside members of the governor’s staff.

At that time, both Hogan and Lt. Gov. Boyd Rutherford tested negative.

The governor has been urging Marylanders consistently to get vaccinated and get booster shots to help blunt the effects of the coronavirus.

Adults are eligible for a booster dose six months after completing initial vaccination with either the Pfizer/BioNTech or Moderna vaccines, or two months after vaccination with Johnson & Johnson.

Teenagers 16 to 18 years old who received Pfizer/BioNTech vaccination also are eligible for a booster shot six months after their initial vaccinations.

Rutherford amplified that message Monday, posting on social media: “I’m glad that he is feeling great right now, because he is vaccinated and boosted. Vaccines are our best defense against #COVID19 and its variants.”