Researchers at the University of New South Wales in Sydney discovered that receiving a booster vaccine dose in the same arm as the initial dose can trigger a faster and stronger immune response. This finding was confirmed through mouse experiments and human clinical trials, as reported by ORF Science.
A study published in the journal Cell offers new evidence that could help improve future vaccination strategies, including insights for developing vaccines that require fewer boosters.
The study found that when administering the first and second doses of a vaccine in the same arm, participants produced antibodies against SARS-CoV-2 significantly faster, within the first week after the second dose. This suggests that the initial effects are not only quicker but also more robust.
The findings derived from mice were then verified with human participants in a clinical study involving 30 volunteers who received the Pfizer-BioNTech COVID-19 vaccine. In the clinical trial, 20 volunteers received both the first and second doses in the same arm, while 10 received the injections in the opposite arm. Approximately four weeks after vaccination, both groups had similar levels of antibodies. The researchers emphasize that patients who received vaccinations in different arms should not worry, as the final level of protection is the same and differences decrease over time.
"Using cutting-edge in vivo imaging technology in mouse experiments, we discovered that when a vaccine is administered, memory B cells move to the outer layer of the nearest lymph node and interact with macrophages there," the research team stated. When a vaccine is administered, specialized immune cells called macrophages are prepared within the lymph nodes, playing a key role in accelerating the immune response.
Upon re-administration of the vaccine in the same limb, macrophages activate B-lymphocytes more quickly, which helps the memory B cells respond more effectively to the booster dose. The research team added, "We also found that additional vaccinations at the same location induce lymph node macrophages to efficiently capture antigens and activate memory B cells, leading to a rapid and strong antibody formation response."
"But this early protection could be vital during an outbreak," noted Mi Ling Munier, head of the Vaccine Immunogenomics Group at the Kirby Institute, emphasizing the importance of initial protective effects during infectious disease epidemics.
"This is a fundamental discovery about how the immune system organizes itself to respond better to external threats—nature has devised this brilliant system, and we are just beginning to understand it," stated Professor Tri Phan, a medical researcher from the University of New South Wales in Sydney and the Garvan Institute of Medical Research, in a press release.
"This study suggests that macrophages in lymph nodes close to the injection site play a central role in inducing effective vaccine responses during the next vaccination," explained Dr. Rama Denny, a co-first author from the Garvan Institute of Medical Research.
In the clinical trial, antibodies demonstrated increased effectiveness against the Delta and Omicron variants. Munier emphasized that the antibodies in the same arm vaccination group were more effective against these variants.
The study's authors noted that while the initial protective effect is crucial during an outbreak, the differences in protection between the two groups decrease over time, alleviating concerns for those vaccinated in different arms.
"Only coronavirus vaccines have been tested so far; other vaccines need to follow," said Phan to the German Press Agency. The team assumes that the findings apply to other vaccinations as well.
"In a pandemic, how quickly protection develops can play a crucial role for the immunity of the population," the research team stated. They believe that these findings could have significant implications for vaccination strategies during infectious disease outbreaks.
According to the research team, vaccine administration is the process of injecting vaccine antigens, which are harmless forms of pathogens, into the body so that the immune system, including immune cells in lymph nodes, recognizes the pathogens and is trained to fight and remember them.
"If we discover ways to reproduce or enhance the interaction between memory B cells and macrophages, we can design next-generation vaccines with fewer booster doses," said Professor Phan.
The research was conducted in mice due to difficulties associated with using human lymphoid tissue samples to assess antibody production. In this study, the research team elucidated the reasons and effects of why memory B cells remain longer in the closest lymph nodes.
The article was written with the assistance of a news analysis system.