Most people are unlikely to have severe allergic reactions to the
-BioNTech vaccine, doctors and vaccine experts say, but the shots might come with temporary side effects such as fever and muscle pain.
Two of the first people to receive the Pfizer-BioNTech Covid-19 vaccine in the U.K. had allergic reactions to the injection, the country’s National Health Service said, spurring questions about the likelihood of such reactions and side effects.
In the coming weeks, U.S. health regulators are expected to authorize the emergency use of two Covid-19 vaccines: one from Pfizer Inc. and BioNTech SE, and another from
While researchers haven’t found serious safety issues with the vaccines, they do come with possible side effects mostly of mild to moderate severity, including fever, fatigue, headache and arm pain. Severe allergic reactions are likely to be rare, they say.
The two people had a history of allergic reactions and carried adrenaline auto-injectors to deal with their allergies. Both recovered after receiving treatment.
The Medicines and Healthcare products Regulatory Agency (MHRA), the body that gave the go-ahead for the Pfizer-BioNTech vaccine in the U.K., has told doctors and hospitals that any person with a history of significant allergic reactions to a vaccine, medicine or food shouldn’t receive the Pfizer-BioNTech vaccine. That includes people with a previous history of anaphylactoid reactions and those who need to carry adrenaline auto injectors.
“As a precautionary measure, the MHRA has issued temporary guidance to the NHS while it conducts an investigation to fully understand each case and its causes. Pfizer and BioNTech are supporting the MHRA in the investigation,” Pfizer said in a written statement.
In its Phase 3 clinical trial, the vaccine was generally well tolerated with no serious safety concerns reported by the independent Data Monitoring Committee, the company said, adding that of the trial’s more than 44,000 participants, over 42,000 have received a second vaccination.
Most people won’t experience severe allergic reactions to the vaccine, doctors and vaccine experts say. They might, however, experience temporary side effects such as fever and muscle pain. Such side effects are signs of something called reactogenicity, health-care providers and vaccine experts say, an indication that the immune system is doing its job. But the likelihood of getting these temporary side effects might be higher than people expect, some vaccine experts say.
The Covid-19 vaccines are “more reactogenic than the flu vaccine,” said
an epidemiologist at the University of Michigan who leads the panel of experts that will advise the FDA about authorizing Covid-19 vaccines. But reactogenicity is perfectly normal, he added, and people shouldn’t be caught by surprise or dissuaded from getting the vaccines, which come in two shots spaced three or four weeks apart.
a participant in a Pfizer and BioNTech vaccine trial and a nursing professor at the University of California, Los Angeles, said the second shot left her with intense arm pain, chills, nausea and dizziness that evening. By the next morning, she had a 104.9-degree fever—the worst she has ever had. She took some acetaminophen, which helped with her fever. A clinical-trial research staffer told her that side effects like hers weren’t uncommon.
While Dr. Choi can’t be sure she received the vaccine—the trial was double-blinded—she suspects she did, and says she wouldn’t have been able to see patients the day after she received the shot.
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“It wouldn’t have been a day I could have gone to work,” she said. “I would have felt too bad to take care of patients.”
Dr. Choi said her symptoms resolved within roughly 36 hours, except for a sore, swollen bump on her arm at the injection site.
The most common side effects found in the Pfizer and BioNTech vaccine trials included pain, redness or swelling at the injection site, fatigue, headache, chills, muscle pain and joint pain, according to a Food and Drug Administration analysis released Tuesday. Side effects tended to be more frequent after the second dose, according to the analysis.
Among those between 18 and 55 years of age, 16% of participants who received the vaccine had fever after the second dose. Fifty-nine percent reported fatigue, 52% reported headache and 35% reported chills. Thirty-seven percent had muscle pain, 22% reported joint pain and 10% reported diarrhea. Those older than 55 tended to report fewer side effects, according to the analysis.
Reactions like Dr. Choi’s are why Northwell Health, which comprises 23 hospitals and nearly 800 health-care practices in New York City, Long Island and Westchester County, N.Y., plans to stagger immunizations among staffers in anticipation of any side effects that could put some out of commission for a day or two.
“For instance, we won’t have all the ICU nurses in one location done in one day—we’ll stagger them out over the course of several days,” said
medical director for Employee Health Services at Northwell Health.
A federal vaccine panel advising the Centers for Disease Control and Prevention recently recommended that health-care workers and residents of long-term care facilities be among the first to receive the vaccines.
‘We’re not really anticipating that we will have a lot of people who will be unable to work because of the vaccine.’
Northwell will also build in a waiting period after every vaccination in the unlikely event that someone has a severe allergic reaction, Dr. Lowe said. But just to be safe, people will be asked to stay in a room for observation—socially distanced—for 30 minutes after they get their shot.
Genesis Healthcare Inc.,
the country’s biggest nursing-home operator, also hopes to stagger staffers at each of its facilities so only one-third of them get shots on any one day, according to
the company’s chief medical officer. He worries that on the day after a vaccine is administered to staffers, a significant number will need to stay home from work because of symptoms. The company will also likely encourage staffers to consider prophylactically taking over-the-counter remedies such as ibuprofen to limit the effects.
The plan echoes the federal vaccine panel’s recommendation that health-care facilities consider the vaccines’ side effects when scheduling vaccinations and avoid vaccinating all workers at once.
A small proportion of participants in the trials of the Pfizer and BioNTech vaccine had side effects such as vomiting and swollen lymph nodes. Researchers identified four subjects who experienced Bell’s palsy, or temporary paralysis of facial muscles, three cases of which were still unresolved by Pfizer’s regulatory submission in November. The FDA said in its analysis that the frequency of Bell’s palsy was consistent with its prevalence in the general population, but the agency said it would recommend surveillance for Bell’s palsy cases when giving the vaccine to larger populations.
A small proportion of vaccine-trial participants classified their symptoms as severe, defined as preventing daily activity, with that happening more frequently after the second dose than after the first. In the case of Pfizer and BioNTech’s vaccine, up to 4.6% of those who received the vaccine reported severe side effects.
Older people and those in long-term care facilities should feel safe receiving the vaccine, said
a professor of geriatric medicine at Florida Atlantic University who works at two elder-care facilities. “The side effects may be uncomfortable for a day or two, but they pale in comparison to getting the virus,” he said, adding that icing the arm and taking acetaminophen can help alleviate any discomfort.
A review of a late-stage Moderna trial found severe side effects included arm pain in 2.7% of participants after the first vaccine dose, according to the company. Severe side effects after the second dose included fatigue in 9.7% and muscle pain in 8.9%, while 5.2% experienced severe joint pain and 4.5% had severe headache.
UCLA’s Dr. Choi said she thinks she was one of the few who experienced the more severe side effects, which can, in some cases, look like symptoms of Covid-19. It is important people understand that the vaccine can’t cause someone to become infected with the coronavirus, she said.
If symptoms such as fever, headache, aches and pains occur shortly after the vaccine, “it’s likely related to the vaccine and not Covid,” she said.
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The anticipated vaccine rollout comes as record Covid-19 case numbers and hospitalizations strain medical resources and staff, heightening the importance of preparing those receiving the vaccines and planning ahead for any possible interruptions to workflow, say people in charge of the vaccine-rollout effort at several institutions.
Houston Methodist recently held a virtual town hall with employees to answer questions about the vaccine rollout, including queries about potential side effects, said
medical director of infection prevention and control.
Recommendations to staffers have included suggesting those who work regular shifts consider scheduling the vaccine before a day off, she said. It is better to be prepared, she said, but she isn’t too worried about the side effects.
“We’re not really anticipating that we will have a lot of people who will be unable to work because of the vaccine,” she said.
—Anna Wilde Mathews and Joanna Sugden contributed to this article.
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