Sometimes it’s the simplest solutions that get lost in the kerfuffle of scientific progress.
Since The advent of vaccines Two hundred years ago, researchers studied all kinds of ways to prime the immune system by inoculating with a weakened pathogen (or its parts) – exploring different doses, vaccination agents and forms of administration.
In all that time, very few experts have examined the question: Which arm should be vaccinated?
Researchers at Oregon Health & Science University (OHSU) suspect this may be the case.
It all started in the early days of the Covid-19 pandemic. Health care workers involved in studies of the immune response to the new Covid-19 vaccines asked experts whether OHSU should switch arms between the first and second jabs.
The team wasn’t sure what advice to give. Until then, most scientists assumed it didn’t matter.
“This question hasn’t really been studied in depth, so we decided to take a look.” He says. Infectious disease expert Marcel Kurlin.
When Curlin and his colleagues searched the scientific literature, they could find only four papers on the topic. The results were mixed.
A randomized controlled trial Among infants, influenza vaccines administered at 2, 3, and 4 months of age resulted in higher antibody titers than those administered in different arms.
A more recent study in 2023However, the covid-19 vaccines had higher immune responses after administration in the same arm as opposed to different arms.
To get clearer data, OHSU researchers tested the antibody levels of 947 participants who received two doses of the Covid-19 vaccine.
Half of the group was randomized to receive the second arm in the same arm as the first, while the other half received staggered jabs in different arms. Four weeks after the second dose, SARS-CoV-2-specific serum antibodies were 1.4-fold higher in those who received the vaccine in different arms.
In 54 pairs, 108 individuals were matched based on sex, age, and vaccination time, and their blood work was compared.
The serum samples collected in the weeks and months after the vaccination showed a clear difference between the groups. Four weeks after the second jab, people who got a shot in both arms had up to a fourfold increase in SARS-CoV-2-specific serum antibodies compared to those who got a shot in only one arm.
Moreover, this improved immune response lasted more than a year after the stimulation.
It turns out to be one of the most important things we’ve found, and it’s probably not limited to covid vaccines. Hypotheses.
“We may be seeing important immune function.”
Curlin and his colleagues aren’t yet sure what that special function is or how it works, but they have an idea.
When the vaccine is administered intramuscularly, the antigens are in the medicine Known for immune cellsHe ‘handcuffs’ the invaders and takes them to the lymph nodes for further questioning. This then benefits the immune system against this specific antigen by sending signals that the invader wants.
The thing is that different parts of the body reach different lymph nodes, so by triggering an immune response on both sides, the body can be more on guard.
“By switching hands, you have memory formation in two places, not one.” He explains Curl
This is the opposite of what the 2023 study found. He suggested that the same arm of vaccines would better prepare the immune system for Covid-19. The reason for the different results may be due to the timing of the serum blood test.
The 2023 study tested blood serum two weeks after vaccinations.
Immune cells that remember the characteristics of the antigen, however, continue to grow and develop for several months after vaccination.
Researchers at OHSU found that after only three weeks, injections in both arms began to show better results than in the same arm, and these benefits increased over time, reaching a peak in the 4th week and persisted for several months.
While more research needs to be done to understand the pros and cons of vaccinating different arms, Curlin said he wouldn’t hesitate to switch to the next booster.
The study was published in Journal of Clinical Investigation.