You can get vaccinated against COVID-19 and the flu at the same time, but is it prudent to do so? This is what science says.

“With the holiday season underway, you may realize that you forgot to get vaccinated against COVID-19 and the flu, especially now that you’ll be sitting in front of your older relatives.

The good news is that it’s still not too late to get the vaccines, but what if we get both at the same time? The Centers for Disease Control and Prevention (CDC) in the United States say it’s a possible option, but should one do it?

A recent Medicare study on claims found a slightly higher, yet still very rare, risk of having a stroke in older people who receive a high dose of the influenza vaccine and the COVID-19 vaccine at the same time.

The risk is about three strokes for every 100,000 doses of Pfizer’s bivalent COVID vaccine and about three transient ischemic attacks for every 100,000 doses of Moderna’s bivalent COVID vaccine. Other studies haven’t found the same risk, leading the CDC and the U.S. Food and Drug Administration (FDA) to state that there are no changes in their vaccine recommendations at this time. The COVID-19 vaccines were updated this year to target one strain of the coronavirus instead of two.

Beyond that, receiving both injections at the same time seems to make it slightly more likely that you’ll experience a temporary reaction to the vaccines. The most common symptoms reported in a government study were fatigue, headache, and muscle pain.

CDC Director, Dr. Mandy Cohen, told CNN that the most important thing is for people to get vaccinated, and the beginning of the respiratory virus season is a good time to do so.

“It’s definitely okay to get several vaccines on the same day,” Cohen said. “I would talk to a doctor or specialized nurse about what’s best for each individual.”

Does doing it at the same time affect protection?
But what about effectiveness? Does the effectiveness of both injections together impact their efficacy?

This is where there might be an advantage.

A small study presented at the recent Vaccines 2023 conference in Boston found that healthcare workers who received the flu vaccines and the bivalent COVID-19 vaccine on the same day had higher antibody responses immediately after receiving them, as well as six months later, compared to people who received their vaccines on different days.

Susanna Barouch, a high school student in Cambridge, Massachusetts, who led the research, said she believes that administering the injections at the same time may stimulate the immune system to react more strongly to the injections. “The flu vaccine could have been an adjuvant for the COVID vaccine,” she said.

But this hasn’t been the only study that looked into the issue, and surprisingly, other studies came to the opposite conclusion or essentially found no difference between administering the vaccines together or separately.

This is one of the first studies to find that co-administration increases antibody levels, and Barouch says that their findings need to be replicated before being accepted as a fact.

“Definitely, I would say this is far from settled,” said Stephen Moss, a researcher at the University of Michigan.

Moss led a recent study that compared the neutralizing antibody responses of 53 Israeli healthcare workers who received their bivalent COVID-19 vaccines separately or with a flu vaccine.

Blood samples from these healthcare workers could equally prevent COVID-19 and flu viruses from infecting cells, whether they received the vaccines together or separately.

A study from the Netherlands, published in June, found that antibodies after joint administration showed significantly lower neutralization capacity compared to a reference group that received their vaccines separately.

Moss said that most co-administration studies have found “a slight increase, a slight decrease, or no change” in antibody levels.

What that means, he claims, is that from a broader public health perspective, it’s probably a good idea to recommend that people receive both at the same time.

“It reduces doctor visits. It reduces the number of encounters with the healthcare system that you must have. It also reduces the number of days you feel unwell after the vaccine. So, you only have to go through that once and not twice,” Moss said.”.