A simple change can greatly enhance the effectiveness of vaccines
Since the advent of vaccines more than two centuries ago, researchers have studied all the different ways that inoculation with a weakened pathogen (or parts thereof) can prime the immune system for a full-scale attack by studying vaccine agents and forms of administration. . Some scientists question whether it matters which group is given the vaccine.
In the early days of the Covid-19 pandemic, health workers involved in studies of the immune response to new vaccines asked researchers at Oregon Health and Science University (OHSU) in the US whether they needed to use different arms for the first and second vaccines. . vaccine doses. However, the research team wasn’t convinced, as most scientists simply assumed it didn’t matter.
“This question has not yet been studied in detail, so we decided to study it,” said infectious disease expert Marcel Kerlin.
When Kerlin and his colleagues reviewed the scientific literature, they found only four studies on the topic. And the results were mixed. A randomized controlled trial in infants showed that at 2, 3, and 4 months of age, influenza vaccination in different groups resulted in higher antibody levels than in the same group. However, a 2023 study showed a higher immune response in the same group after receiving the COVID-19 vaccine.
To get a clearer picture, OHSU researchers looked at antibody levels in 947 participants who received two doses of the COVID-19 vaccine. Half of the group received a second dose in the same group, and the other half received a second dose in both groups. Four weeks after receiving the second dose, serum antibodies to SARS-CoV-2 were 1.4 times higher in those who received the vaccine in the different groups.
The researchers then measured antibody levels in 54 pairs matched for age, sex, and time between vaccinations. Four weeks after receiving the second dose, those vaccinated in both groups had a fourfold increase in antibodies against SARS-CoV-2 compared to those vaccinated in only one group. Moreover, this improved immune response persisted for more than a year after the booster dose.
“This turned out to be one of the most important discoveries, and it’s probably not limited to just the COVID vaccines,” Kerlin suggested.
The researchers aren’t yet sure why this happens, but they suggest that changing the hand that receives each dose triggers new immune responses in different lymph nodes.
“By switching hands, you’re essentially building a memory in two places instead of one,” Kerlin explains.
However, a 2023 study came to the opposite conclusion, finding that vaccination in one group better prepares the immune system for COVID-19. The reason for the different results may be related to the time of blood analysis. A 2023 study looked at blood serum just two weeks after receiving the vaccine. However, immune cells that remember the characteristics of the antigen continue to grow and mature for many months after vaccination.
Kerlin said further research is needed and it is too early to make clinical recommendations based on the results of this study, which was published in the Journal of Clinical Investigation.
