Covid injections may slightly increase stroke risk in older recipients | ET REALITY


The Covid vaccines made by Pfizer-BioNTech and Moderna may be linked to a slight increase in the risk of stroke when given alongside a high-dose flu vaccine, according to a study. new analysis by the Food and Drug Administration.

The high-dose flu vaccine is generally given to older people and the risk association is clearest in adults 85 years of age and older. But that increase, if real, seems very small, and it’s possible that the risk comes only from the flu vaccine.

TO separate analysis by the agency points to a small increase in the incidence of seizures after the Covid vaccine in children aged 2 to 5 years. The papers were published online last week and have not yet been vetted for publication in a scientific journal. Vaccine safety experts said the studies were well done.

Neither study is definitive, and even if these links are confirmed, the increases are so slight that the benefits of vaccination still far outweigh the risks, especially in older adults, experts said. Both the flu and Covid increase the risk of having a stroke.

Although the findings do not justify a change in vaccine recommendations, they are suggestive enough to merit further study, experts said.

“Without these kinds of efforts, the absence of data, the absence of evidence, just leads to a lot of misperceptions,” said Dr. Susan Cheng, a cardiologist and epidemiologist at the Smidt Heart Institute at Cedars Sinai in Los Angeles.

The FDA did not make the researchers available for interviews. In a statement, Cherie Duvall-Jones, a spokesperson for the agency, said she was “releasing this information at this time by publishing this document for greater transparency.”

Both studies are based on observational data, which cannot identify cause and effect. The agency plans study the occurrence of seizures in children after vaccination “using a more robust design,” Duvall-Jones said.

“Sometimes similar small associations of increased risk are not confirmed by additional investigation,” he added.

Giving flu and Covid vaccines at the same time, or with a single shot combining both, once one is available, is an increasingly popular strategy among health officials seeking to increase uptake of the vaccine. vaccine and ease logistical burdens, said Marco Cavaleri, who heads the European Medicines Agency’s Office of Biological Health Threats and Vaccines Strategy.

“That is the way of the future,” Dr. Cavaleri said. “Of course, we must be sure that this is a good strategy also from a security point of view.”

Dr. Cavaleri said he was still not convinced that the increased risk of stroke was real. Strokes and related health problems occur frequently among people age 85 and older, he noted. “We have to be extremely careful and not overinterpret the data before we get really large data sets, maybe from different regions, that can tell us exactly what’s going on,” he said.

U.S. officials first noted a possible partnership about a year ago. At the time, data from the Vaccine Safety Datalink, a federal safety monitoring system, suggested that Americans age 65 and older could be at increased risk of having an ischemic stroke, which cuts off blood supply to the brain, within 21 days after receiving the Pfizer vaccine. BioNTech’s bivalent vaccine was offered last fall.

But federal officials said in January that further investigation suggested a link was “very unlikely” and that other surveillance systems, including those in other countries, had not found a connection.

In the new study, researchers from the FDA and the Centers for Medicare and Medicaid Services analyzed the risk of stroke among nearly 5.4 million Medicare beneficiaries age 65 and older. They examined the health records of those who received a bivalent Covid injection, either alone or together with the flu vaccine, between August 31 and November 6, 2022.

Their initial analysis found no statistically significant increases in strokes with Covid vaccines given alone. When federal researchers broke down the data by age, they found an increased risk of stroke among those who were 85 years old or older and received the Pfizer-BioNTech vaccine, and among those who were 65 to 74 years old and received the Moderna vaccine.

The link was most consistent when the bivalent Covid shot was given at the same time as a high-dose flu vaccine or one containing an adjuvant, a chemical added to trigger a stronger immune response.

Those who received both the Covid vaccine and the flu vaccine experienced a 20 percent increase in the risk of ischemic stroke with the bivalent Pfizer-BioNTech shot, and a 35 percent increase in stroke risk Transient ischemic stroke after bivalent injection of Moderna. (The bivalent injections were replaced in September by new formulations.)

Researchers then took a closer look at the relationship between the flu vaccine and stroke in nearly 7 million Medicare participants who received a high-dose or adjuvanted flu vaccine. They found a small but statistically significant increase, about 9 percent, in the risk of stroke after receiving the flu vaccine alone.

The results suggest that the high-dose flu vaccine may be responsible for the increase in strokes seen in the study, said Daniel Salmon, director of the Institute for Vaccine Safety at the Johns Hopkins Bloomberg School of Public Health.

However, the study found some strange patterns, for example, an increased risk of some types of stroke with the flu vaccine in people aged 65 to 74 and in those aged 85 and older, but not among those 75 to 84 years old.

“That’s the kind of thing that would make me wonder if there might be something strange going on in your data, because you would expect there to be more consistency,” Dr. Salmon said.

Federal researchers also calculated a separate measure called attributable risk, or the increased risk that can be attributed to the exposure. Except for people aged 85 and older, the attributable risk was approximately three additional cases of stroke per 100,000 people vaccinated with the Covid vaccine.

The numbers are too small to warrant alarm, Dr. Salmon said, especially since the diseases themselves also carry a risk of stroke.

“If I told you that your risk of being struck by lightning doubled, to be honest, I wouldn’t worry too much, because your risk of being struck by lightning is pretty small,” he said. “Because the background rate is so small, doubling that risk isn’t much.”

Experts also said they were not surprised or concerned by the findings about seizures among vaccinated children.

In that study, FDA researchers analyzed the incidence of 21 health outcomes in more than 4.1 million children after immunization with the original Covid-19 vaccines made by Pfizer-BioNTech, Moderna and Novavax.

The researchers based their analysis on commercial claims in insurance databases, as well as vaccination data from state and local systems.

The analysis confirmed a previously observed risk of rare heart problems after Pfizer-BioNTech Covid injections in children ages 12 to 17.

The study also found a small increase in the incidence of seizures and convulsions after the Moderna or Pfizer-BioNTech shots, but only among children ages 2 to 5.

A consistent trend in seizures across all age groups would have been more concerning. But young children are prone to seizures when they have a high fever, Dr. Cheng said, and other fever-producing vaccines are known to induce seizures in very young children.

“We know that Covid vaccines can cause fever, so it’s not a very surprising finding if it’s true,” Dr. Salmon said of seizures.

Children are at much lower risk of contracting Covid than older adults, so many parents have chosen not to vaccinate them. The low numbers make it difficult to study potential risks, experts said.

“I commend them for doing the job,” Dr. Salmon said of the FDA investigation. “I wish they had been done sooner, but it’s great that the studies are being done.”

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