Research Finds Stronger Vaccine Protection from Alternating Arms

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Feb. 6, 2024 -- People who alternated arms when receiving multiple shots of the COVID-19 vaccine saw an improved immunity response, according to new research.

The research was published in The Journal of Clinical Investigation.

The boost, compared to people who use the same arm for two shots, could be significant for some people who don’t respond well to vaccines because of age or health conditions, The New York Times reported. 

“At this point in the pandemic, with most people having had multiple vaccine doses or infections, alternating arms for Covid vaccines may not offer much benefit,” The Times wrote. “Yet if confirmed by further study, the results could have implications for all multidose vaccines, including childhood immunizations.”

“I’m not making recommendations at this point, because we need to understand this a lot better,” said Marcel E. Curlin, MD, an infectious disease physician at Oregon Health & Science University, who led the work.

But “all things being equal, we ought to consider switching up the arms,” he told The Times.

Previous studies were small and produced varying results. None showed a major difference in the immunity provided.

In Curlin’s study, he and others repeatedly measured antibody levels in 54 pairs of university employees matched for age, gender, and time after vaccination. 

They found that switching arms increased blood antibody levels by up to four times. 

Curlin called the effect “consistent (and) statistically significant.”

“The improved response clearly materialized three weeks after the second booster and persisted beyond 13 months after boosting,” Oregon Health & Science University said in a press release. “Investigators found heightened immunity to the original SARS-CoV-2 strain, and an even stronger immune response to the omicron variant that emerged roughly a year after arm alternation.

“Researchers aren’t sure why this happens, but they speculate that giving a shot in each arm activates new immune responses in different lymph nodes in each arm.”