Sometimes the simplest solutions get lost in the chaos of scientific progress.
Since then, The advent of vaccines More than two centuries ago, researchers studied all sorts of ways in which the immune system could be primed for a full attack by inoculating with weakened pathogens (or parts of them), using various doses, vaccine agents, and forms of administration. I've been researching.
In the meantime, few experts have investigated the question: “Does it matter which arm gets vaccinated?”
Researchers at Oregon Health & Science University (OHSU) think it might be possible.
It all started in the early days of the COVID-19 pandemic. Healthcare workers taking part in a study into the immune response to COVID-19 vaccines had asked OHSU experts whether they should switch weapons between the first and second jab. .
The team didn't know what advice to give. Until then, most scientists thought it didn't matter.
“This issue hasn't been studied in much detail, so I decided to look into it.” To tell Infectious disease expert Marcel Carlin.
When Karlin and colleagues combed through the scientific literature, they found only four papers on the topic. And the results were mixed.
1 randomized controlled trial Among infants, antibody levels were found to be higher when children received influenza vaccinations in different groups at 2, 3, and 4 months of age than when vaccinated in the same group.
More recent research in 2023However, the researchers found that immune responses were higher after COVID-19 vaccination in the same treatment group, as opposed to different treatment groups.
To get a clearer picture, OHSU researchers tested antibody levels in 947 participants who received two doses of the COVID-19 vaccine.
Half of the cohort was randomized to receive the second dose in the same arm as the first, while the other half received the staggered jab in a different arm. Four weeks after the second dose, SARS-CoV-2-specific serum antibodies were 1.4 times higher in vaccinated people in different groups.
A subset of 108 people in 54 pairs were matched based on gender, age and vaccination period, and blood tests were compared.
Serum samples taken weeks and months after vaccination showed clear differences between the groups. Four weeks after the second jab, SARS-CoV-2-specific serum antibodies increased by up to four times in people who received injections in both arms compared to those who received injections in only one arm.
Furthermore, this improved immune response persisted for more than 1 year after the booster immunization.
“This turns out to be one of the most important things we discovered, and it's probably not just limited to COVID-19 vaccines,” Carlin said. Make a hypothesis.
“We may see important immunological functions.”
Karlin and his colleagues don't yet know what that special feature is or how it will work, but they have an idea.
When the vaccine is administered into the muscle, the antigen contained in the drug is recognized by immune cells, “handcuffs” the intruder and takes him to the lymph node for further interrogation. This stimulates the immune system against this specific antigen by sending the desired sign of the invader.
Importantly, different sides of the body drain into different lymph nodes, which can cause an immune response on both sides, making the body more alert.
“When you switch arms, you basically form memories in two places instead of one.” explain Carlin.
This is the opposite of the 2023 survey results. It suggested that vaccinating people in the same arm could better prepare their immune systems against COVID-19. The reason for the different results may be due to the timing of the serum blood test.
A 2023 study tested serum just two weeks after vaccination.
However, immune cells that remember antigen characteristics continue to proliferate and mature for months after vaccination.
OHSU researchers noticed that injections into both arms began to show better results than the same arm after just three weeks, and the effects gradually improved, peaking at four weeks, and continued for months afterward. It also lasted.
More research is needed to understand the pros and cons of different vaccinations, but Karlin said he wouldn't hesitate to switch to the next booster.
This study clinical research journal.
