The immune response can be increased fourfold when people alternate arms when given a multiple dose vaccine.
- Switching arms improves the effectiveness of two-dose vaccinations, a new study suggests.
- Three weeks after the second dose, significantly higher numbers of antibodies capable of binding to and neutralizing the SARS-CoV-2 virus were observed in blood samples.
- Rates gradually increased over the four weeks, from 1.3 to 4 times against the Omicron variant.
Want to boost your immunity? Just switch arms when you get vaccinated. This was recently suggested by researchers at Oregon Health & Science University (United States). To achieve this discovery, the team carried out a study in which they measured the antibody response in the blood of 947 people who received two doses of Covid-19 vaccine at the start of the pandemic.
In detail, the volunteers, who included university employees, agreed to be vaccinated against the coronavirus for the first time. Then they were randomly assigned to receive the second dose in the same arm or the opposite arm. The scientists analyzed blood samples taken at different times after vaccination.
Alternating arms for each dose increased the number of antibodies capable of neutralizing Covid-19
Until now, doctors thought that the choice of arm did not matter. However, the results, published in the journal Journal of Clinical Investigation, showed an increase in the magnitude and breadth of the antibody response in participants who received an injection in each arm compared to those who did not. The improvement in the immune response was evident three weeks after the second vaccine and persisted beyond 13 months after the booster.
According to the researchers, increased immunity against the original SARS-CoV-2 strain and an even stronger immune response against the Omicron variant emerged about a year after injection in each arm.
Vaccine: “by passing from one arm to the other, memory is formed in two places instead of one”
At this time, the authors are not sure why this happens, but they speculate that giving one dose in each arm activates new immune responses in different lymph nodes in each arm. “By moving from one arm to the other, the memory is formed in two places instead of one”, has explained Dr. Marcel Curlinauthor of the work.
Although this study focused on Covid-19 vaccination, the team says they expect the improvement in immune response to be similar for other multiple-dose vaccines. To confirm this, they believe additional research needs to be conducted.