by If you have submitted the same group for each dose of a particular vaccine, you may want to reconsider. Alternate arms can produce a more powerful immune responsesuggests a new study.
The researchers studied responses to the first two doses of the Covid-19 vaccines. Those who alternated arms showed a small increase in immunity over those who received both doses in the same arm.
For people who respond poorly to vaccines because of their age or health conditions, even a small booster can be meaningful, the researchers said. At this point in the pandemic, where most people have received multiple doses of vaccines or have had infections, alternating arms for Covid vaccines may not offer many benefits.
However, if confirmed by further studies, the results could have implications for all multi-dose vaccines, including childhood ones.
“I’m not making recommendations at this time, because we need to understand this much better,” said Dr. Marcel E. Curlin, an infectious disease physician at Oregon Health and Science University, who led the work.
But “all things being equal, we should consider changing weapons.”
The few studies that compare the two approaches they have been small and have produced mixed results. AND Neither study showed a big difference. in immunity.
A study in mice found that a single lymph node can generate strong immunity after vaccination, said Jennifer Gommerman, chair of the department of immunology at the University of Toronto, who was not involved in the new research.
“This means that the lymph nodes are really good at their job,” he said, and most vaccines will work well if they target just one arm.
In most people, extending the interval between doses (to three to four months, as was done in Canada for Covid shots, rather than the three to four weeks recommended in the United States) may offer greater benefit than change arms, Dr. Gommerman said.
Still, all of these strategies are worth studying, because in immunocompromised people “anything that helps their immune responses is worth doing,” he added.
In the new study, Dr. Curlin and his colleagues repeatedly measured antibody levels in 54 pairs of university employees matched for age, sex, and time after vaccination.
Participants, part of a larger research project, were randomly assigned to receive the second dose in the same arm as the first dose or in the opposite arm. The researchers excluded anyone who became infected with Covid during the study.
The scientists found that switching arms increased blood antibody levels by up to four times. The results were published in The Journal of Clinical Investigation.
The immune response was stronger against both the original coronavirus and the Omicron variant, which emerged about a year after the first Covid vaccines were authorized.
“It is a consistent and statistically significant effect; It is quite large; and it seems pretty durable,” Dr. Curlin said.
At first, the results seem to contradict those of a German study last summer that showed that rolling up your sleeves each time could produce a better immune response. But that study measured antibody levels just two weeks after the second dose.
In that period, the new study also found similar results. But the pattern slowly changed over the following months to higher antibody levels in those who switched arms.
The results of the new study did not entirely surprise the German researchers.
“What you see is an option that I had in mind as a possibility, so it’s interesting that you actually see this kind of change in effects,” said Martina Sester, an immunologist at the University of Saarland in Saarbrücken, Germany.
Switching arms with each dose could be “one part of many measures that could easily be taken to perhaps lead to a successful immune response,” Dr. Sester said.
