(CNN) On the long-awaited January morning when members of the nation's largest police department became eligible for Covid-19 vaccinations, hundreds flocked to get the shot.
"We've been ready to go for some time," NYPD Commissioner Dermot Shea said at the time, describing the rank and file as "definitely eager" to get vaccinated but acknowledging "some hesitancy."
"It's going to take some momentum," said Shea, who himself contracted the virus and recovered at home.
Four months later, 40% of the NYPD's roughly 36,000 officers and 19,000 civilian employees had received at least one dose of the Covid-19 vaccine, according to department spokesperson Sgt. Edward Riley. That's nearly 20% less than the percentage of New York City adults with at least one shot.
"This is reflective of what many other police agencies are seeing," Riley said via email. "Since vaccines became available we have encouraged our employees, especially those who have contact with the public, to get vaccinated."
In big cities across the country, law enforcement agencies gave a hodgepodge of responses to questions about vaccination rates. Many reported rates lower than or comparable to the rest of the population. In some places officers are not required to report having been vaccinated.
The vaccine reluctance among officers comes after a year in which Covid-19 was the biggest killer of law enforcement in the United States, accounting for at least 145 line-of-duty deaths, according to preliminary data from the National Law Enforcement Officers Memorial Fund. That's more than double the number of officers killed by heart attacks, shootings, drownings, car crashes or other causes combined -- one of the deadliest years for law enforcement in history.
"There has definitely been some hesitancy among a group of officers, much like you're seeing in the rest of society," said Chuck Wexler, executive director of the Washington nonprofit Police Executive Research Forum.
"I think there's a general concern, principally among younger officers, that they think they need to know more."
As of Tuesday afternoon, 47.7% of the US population had at least one dose of a Covid-19 vaccine, and about 37.5% was fully vaccinated, according to the US Centers for Disease Control and Prevention.
Nationwide as of Tuesday 60% of eligible adults 18 and over have received at least one dose and 47.6% have been fully vaccinated, according to the CDC.
Vaccine hesitancy among law enforcement officers raises concerns over their potential to spread the virus during interactions in communities they are sworn to protect.
"It poses a potential readiness problem should we have another pretty heavy wave here in the city of Covid infections," said Warren Eller, chair of the pubic management department at John Jay College of Criminal Justice in New York. "It might even locate some of them as being vectors."
"Unvaccinated cops may actually become a disease factor for some period of time, especially if they are asymptomatic," Eller added.
The national Fraternal Order of Police, with more than 356,000 members, in a statement urged federal and state governments to make law enforcement a priority in vaccination access.
"However," the nation's largest police union said, "the decision to receive the vaccine is an individual one."
Police agencies gave disparate responses to vaccination efforts.
In Ohio, for instance, Columbus Division of Police -- the largest department in the state -- said 28% of its 1,800 sworn personnel had received at least their first shot by early May but that officers were not required to report their status so more may have gotten a shot.
In Georgia, the South Fulton Police Department reported fewer than 50% of its employees -- 134 sworn officers and 19 civilians -- have been fully vaccinated.
"We're going to try to continue to educate our people to try to get more officers comfortable," Police Chief Keith Meadows said. "It's even more important, to be perfectly honest with you, that our officers are educated around this issue."
Like many people around the country, South Fulton Det. Joseph King has chosen to wait on the shot.
"I just want to kind of stand back and let them work the kinks and I'll make a decision later on ... Do I want to go and take the vaccine?" he said.
The Cincinnati Police Department is "strongly encouraging" employees to get the shot but does not require them to report vaccination status, according to Lt. Steve Saunders.
In Nevada, the Las Vegas Metropolitan Police Department reported earlier this month about 40% of its more than 5,700 employees had received the first dose -- and 39% had gotten the second shot or the single dose Johnson & Johnson vaccine.
"I made the decision to go ahead and get the vaccine in hopes that I don't have to feel that way again," said Steve Grammas, president of the Las Vegas Protective Police Association, referring to the three weeks he was sick with the virus last year.
In Pennsylvania, the Philadelphia Mayor's office said the city was tracking the preliminary rates internally but not releasing specific agency data at this time.
Suffolk County, in the New York suburb of Long Island, reported earlier this month that 51% of all police department and sheriff's office employees and 47% of all law enforcement had received at least one vaccine.
In California, about 50% of the Los Angeles Police Department's roughly 9,000 officers and 3,000 civilian employees have received at least one dose -- and 40% had gotten both doses as of May 3, according to Sgt. Heidi Stoecklein.
In Maryland, the Baltimore Police Department reported Tuesday that 62% of its nearly 3,100 civilian and sworn personnel had at least one dose. The department recently launched an internal "Don't wait. Vaccinate" campaign with posters of civilian and sworn members who have received the shot.
In Illinois, the Chicago Police Department said 6,896 doses had been administered to members of its 12,000-officer force as of late April, and 3,581 employees had received at least one shot. This does not include vaccinations administered by private health care providers.
"It was painless and I am afraid of needles, but I didn't feel a thing," Chicago Police Superintendent David Brown said after receiving his vaccine on camera earlier this year.
John Catanzara Jr., president of Fraternal Order of Police Chicago Lodge No. 7, said he isn't surprised by the vaccination rate.
"I think the officers are no different than the general population," he said. "There's a skepticism."
In Oregon, 62% of the Portland Police Bureau's more than 800 sworn members had received a first dose as of this week, according to Terri Wallo-Strauss, who said the city is not tracking who gets the vaccine and the numbers may be higher.
Phoenix, Arizona, is not requiring public employees to share their vaccination status but city spokesman Dan Wilson said workers were being encouraged to get the shot through a one-time $75 vaccine safety award. The city has processed 1,114 awards -- as of Tuesday -- for the police department, which has 3,982 sworn and civilian employees.
The NYPD has made vaccines available to officers "at multiple times and at multiple locations," according to Riley. The department has also produced and distributed multiple videos encouraging employees to get vaccinated.
Riley said that while "upwards of 11,000" department members have been previously infected and thus "have a far lower likelihood of re-contracting the disease," the NYPD has been focused on dispelling rumors and misinformation regarding vaccination.
"While we have stopped short of compelling uniformed officers to be vaccinated by rule -- which would likely face lengthy legal challenges -- we have focused our efforts on strong education and encouragement," he said.
"Everything is done on a voluntary basis. Everyone is an individual. Every officer has a different view," Mayor Bill de Blasio said recently when asked about the low NYPD vaccine rate.
"Like many, many New Yorkers, I think there are some people that just wanted to wait a while," he added. "There are some people that just have unanswered questions. We've got to keep reaching out and answering the concerns."
Eller said the vaccination rates for law enforcement don't seem significantly different from those of the general public.
"There's the question of, 'What is it that can be required of folks in a position of authority?' " he said. "There are a number of challenges there. We also don't know how many of these officers were previously infected. Some folks are not getting vaccinated because they have some skepticism about the process, efficacy. Some folks are just holding off on vaccination because they were infected pretty early on and believe that they carry some residual immunity, which gives them a little bit of time."
Late last month, Officer Michael Mundy became the 55th member of the NYPD whose death was related to Covid-19, a senior law enforcement official told CNN.
In an internal department email, obtained by CNN, Shea said the Brooklyn resident had been assigned to the 77th Precinct and joined the force on July 11, 2001.
"For nearly 20 years, he served the people of Brooklyn — and New York City, as a whole — with great distinction," Shea said in the email.