Switching Arms for the Second Dose of a Vaccine Significantly Enhances Its Effectiveness

Published by Cédric - Thursday, February 22, 2024 - Other Languages: FR, DE, ES, PT
Article Author: Cédric DEPOND
Source: The Journal of Clinical Investigation

New research has revealed a significant boost in immune response when individuals switch arms for the administration of a multi-dose vaccine. This simple act could quadruple the vaccine's effects.

The laboratory study, led by researchers from the Oregon Health & Science University (OHSU), measured the antibody response in the blood of 947 individuals who received two-dose vaccinations against COVID-19 at the onset of the pandemic. The participants included OHSU employees who agreed to enroll in the research while being vaccinated against the SARS-CoV-2 virus and were randomized to receive the second dose in the same arm as the first dose or in the opposite arm.


Illustration Image Pixabay

Historically, clinicians believed that the choice of arm did not matter. However, the new study, recently published in The Journal of Clinical Investigation, tested serum samples collected at different times after vaccination. They found a substantial increase in the magnitude and scope of the antibody response in individuals who received a "contralateral" vaccination - an injection in each arm - compared to those who had injections in the same arm.

The improvement in immune response was clearly evident three weeks after the second booster and persisted beyond 13 months post-boost. The researchers found increased immunity against the original strain of SARS-CoV-2 and an even stronger immune response to the omicron variant that appeared about a year after switching arms.

The researchers are uncertain about why this occurs but speculate that administering an injection in each arm activates new immune responses in different lymph nodes of each arm. "By switching from one arm to the other, you essentially have memory training in two places instead of one," stated lead author Marcel Curlin, an associate professor of medicine (infectious diseases) at the OHSU School of Medicine and medical director of OHSU Occupational Health.

The study has generated significant interest as it offers perspectives for enhancing the effectiveness of two-dose vaccines, not only against COVID-19 but potentially for other multiple-dose vaccinations. Although this research focused on COVID-19 vaccination, the researchers indeed assume that the results could be similar for other multi-dose vaccines. They call for further research to determine if contralateral vaccination improves immune response for other vaccines, especially in children.

It is important to note that this study raises promising questions, but it is too early to make clinical recommendations based on its findings. However, this discovery could significantly impact how vaccinations are administered in the future, potentially offering a valuable boost in immunity for vaccinated individuals.
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