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MGH vaccinating workers against monkeypox, the first time the shots have been used in the US

Massachusetts General Hospital this week began vaccinating a small group of workers against monkeypox who were in close contact with a man diagnosed with the virus and hospitalized at MGH.Josh Reynolds/For The Washington Post

Massachusetts General Hospital this week began vaccinating a small group of workers against monkeypox — the first time the new medicine has been used in this country outside of clinical trials.

The workers were in close contact with a man diagnosed with the virus and hospitalized at Mass General from May 12 to May 20. The patient was the first person in the United States to be tied to an ongoing outbreak of the rare virus in Europe and North America.

Monkeypox has now been identified in nine people across seven states, including Massachusetts, Florida, Utah, Washington, California, Virginia, and New York, the Centers for Disease Control and Prevention said Thursday. Among the latest cases, reported Thursday by health officials in Virginia, is a woman who recently traveled to an area in Africa where the disease is known to occur. They said she was not infectious during travel and did not require hospitalization.

Globally, more than 370 cases have been reported in the outbreak since the first puzzling cluster appeared in the UK last month.


At Mass General, teams of specialists have been working long hours tracking down each person believed to have been in contact with the patient to determine whether they may have been exposed to infection and, if so, their level of risk. That includes everyone from doctors and nurses to those who may have briefly delivered a meal tray just inside the door.

“This certainly felt novel because this was the first time we were able to use [the monkeypox vaccine] in response to an outbreak,” said Dr. Paul Biddinger, chief preparedness and continuity officer for Mass General Brigham.

MGH workers received the JYNNEOS vaccine, developed by Danish company Bavarian Nordic and approved in the US in 2019.

Dr. Brett Petersen, deputy chief of the CDC’s Poxvirus branch, confirmed in a statement that the Mass General initiative was pioneering.


“We can confirm this is the first one of JYNNEOS outside of clinical trials in the U.S,” Petersen said.

A spokesperson for Bavarian Nordic, which manufactures JYNNEOS, said Thursday that the US has more than 1 million doses stored between the government’s stockpile and with Bavarian Nordic in Denmark.

Because monkeypox is so rare outside of Africa, and the drug was only approved in the US recently, health officials are still learning about how effective JYNNEOS might be in protecting against monkeypox after someone has been exposed. The shots are designed to be given before exposure.

“We have no rigorous studies in humans and little real world experience,” Petersen said.

“However, JYNNEOS induced a rapid, robust antibody response in clinical trials and limited animal studies suggest it is effective as post-exposure prophylaxis as well,” he said.

In general, the sooner the vaccine is administered after an exposure, the higher likelihood of success, Petersen said.

“The effect of ... timing in relation to exposure is something we are interested in following and learning more about to inform optimal use of this vaccine,” he said

A CDC official earlier this week said as many as 200 people may have come in contact with the MGH patient, but said the vast majority of them were health care workers.

That meant calls and long discussions with each worker to determine exposure, and then a second conversation for anyone offered the vaccine about its benefits and risks.


“It’s been quite labor intensive,” Biddinger said.

“It took a huge number of people working all last week and through the weekend to make sure we could deliver the vaccines to those who wanted it and needed it,” he said.

Monkeypox is transmitted through close skin-to-skin contact that involves bodily fluids, or indirect contact, such as contaminated bedding materials, with fluid from the lesions the virus produces. It can also be transmitted through respiratory droplets when a patient has lesions in the mouth.

Biddinger said officials separated the pool of workers thought to be exposed into three groups: those believed to have very low exposure, those with intermediate risk, and those at high risk. The pool also included anyone who may have been exposed but who does not work at Mass General, such as visitors to the room the patient was in before he was isolated, Biddinger said.

Fewer than 10 people were in the high risk category, and less than 50 in the intermediate pool, he said. Ultimately some who were offered the shots declined, and, to date, fewer than 10 have been vaccinated, Biddinger said.

JYNNEOS is administered in two doses, four weeks apart. It has considerably fewer potentially serious side effects than an older vaccine, Acam2000, approved in the US for smallpox. Acam2000, which is comprised of a live, replicating pox-type virus, is thought to be protective against monkeypox, too, but its prescribing label says it can produce serious heart problems, brain swelling, skin infections, and, potentially, blindness.


Biddinger said Mass General worked closely with the CDC and the state health department to develop communication and counseling materials for people who have been offered the new JYNNEOS vaccine, which is not made with replicating virus, and lists headache, fatigue, and muscle pain as among the most common potential side effects.

“It has been a real, real-time learning effort,” he said.

Kay Lazar can be reached at Follow her @GlobeKayLazar.