A study presented at Vaccines Summit Boston suggests getting a flu shot and a COVID-19 booster on the same day “may yield higher and more durable” antibody responses.
The antibody levels of 42 previously vaccinated health care workers were measured in the study. Of the 42 workers, 12 received their flu shot and bivalent COVID-19 booster on the same day, and the other 30 received them on different days of the same month.
Evidence of sustained increased antibody levels
Roughly a month after the health care workers received COVID-19 boosters, antibody tests showed that those who received the booster and the flu shot on the same day had higher IgG1 levels.
IgG1 is an antibody that protects the body from harmful bacteria and viruses, per Science Direct. The antibody recognizes antigens, attaches itself to them and signals the immune system to respond. This antibody is also crucial to fighting against COVID-19, NBC reported.
The same health care workers were later tested again, and the raised antibody levels remained raised six months after injection.
A senior scholar at the John Hopkins Center for Health Security, Amesh Adalja, told The Guardian the increase in IgG1 is “possibly due to enhanced stimulation of the immune system by both vaccines being present at the same time.”
“The key thing is to see if this has any kind of meaningful clinical benefit — do the higher levels of antibody translate into more protection against infection or disease?” Adalja continued.
The chief of infectious diseases at Penn Presbyterian Medical Center in Philadelphia, Dr. Judith O’Donnell, added, “We probably would want to see this kind of data replicated using the current 2023 vaccines to really know with 100% certainty how giving those together might enhance immunity or not.”
Greater side effects
JAMA Network published an analysis of self-reported data from nearly 1 million individuals 12 years of age and older who received flu and COVID-19 booster shots on the same day. Of these individuals, 8% to 11% reported higher “systemic reactions” to the dual injection.
The CDC commented, “People who got a flu vaccine and COVID-19 monovalent vaccine at the same time were slightly more likely to have reactions including fatigue, headache, and muscle ache than people who only got a COVID-19 monovalent vaccine, but those reactions were mostly mild and went away quickly.”
Though the CDC encourages the public to receive COVID-19 boosters and the flu shot on the same day, it’s to increase efficiency in administration, not due to medical reasoning.
The CDC added that receiving both shots at once is safe, and though reactions are somewhat increased, they “were mostly mild and went away quickly.”