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Yahoo
30-04-2025
- Health
- Yahoo
Which Arm Gets Vaccinated Could Play a Role in Your Immune Response
The arm you offer up for vaccination could impact your immediate immune response. But here's the catch: scientists still aren't sure if it's better to give a secondary booster shot to the same arm or a different one. Currently, only a handful of studies have explored whether you should switch sides between a first and second jab, and the ones on COVID vaccines have produced mixed results. Following the 2020 outbreak of COVID-19, for instance, researchers in Germany found that giving multiple jabs to the same arm produced better immune responses two weeks later. Then, a follow-up study from researchers in the US found the exact opposite. According to that randomized trial, switching arms between shots resulted in a four-fold increase in COVID-specific antibodies four weeks after the second jab. Get ready for yet another contradictory finding. Researchers in Australia are weighing in on the debate, and their experiments on mice and humans agree with the same-arm study. The trial, led by Rama Dhenni from the Garvan Institute of Medical Research and Alexandra Carey Hoppé from the University of New South Wales (UNSW), involved 30 healthy participants who had not yet had COVID-19. All participants received two shots of the Pfizer vaccine, three weeks apart – 20 had both shots in the same arm, while 10 got the booster in the opposite arm to the first jab. Those in the same-arm group showed a boosted immune response in the week after their second shot, according to blood and lymph node analysis. "Those who received both doses in the same arm produced neutralizing antibodies against SARS-CoV-2 significantly faster – within the first week after the second dose," explains Carey-Hoppé. "These antibodies from the same arm group were also more effective against variants like Delta and Omicron," adds immunologist Mee Ling Munier from UNSW. Still, the apparent immune boost from a same-arm vaccination was ultimately short-lived. Four weeks after the booster, those who received a jab in the same arm showed similar antibody levels to those who received a jab in the opposite arm. This suggests that the strengthened immune response from same-arm vaccinations does not last longer than a month. "If you've had your COVID jabs in different arms, don't worry – our research shows that over time the difference in protection diminishes," says Munier. "But during a pandemic, those first weeks of protection could make an enormous difference at a population level." Further research is needed, but Munier suspects that this same-arm vaccine strategy could help achieve herd immunity faster. To explore why that might be, Munier and colleagues used mouse models. When mice were given a second vaccine to the same side of the body, it increased their immune response in that side's lymph nodes. Lymph nodes drain fluid from their respective sides of the body. When a vaccine is administered to one arm, it introduces the corresponding lymph node to a weakened pathogen (or its components). Immune cells called macrophages, which guard the entry point to the lymph nodes, handcuff these invaders and take them to unique players called memory B cells (Bmems). These long-lived cells memorize what the danger looks like for future reference, and they also enter a specialized factory within the lymph node to trigger the production of antibodies tailored to that specific invader. In mouse models, when a second vaccine was given to the same side of the body, the draining lymph node's sentinel macrophages were already primed to respond to that threat. This means they jumped to action faster, communicating with "large clusters of reactivated Bmems" to send 10 times as many Bmems into the antibody factory as the non-draining lymph node. Similar to the mouse data, when 18 of the human participants had their lymph nodes biopsied with a fine needle, the researchers found those who received a same-arm jab had increased percentages of Bmems in these antibody factories. While these results are intriguing and shed some much-needed light on how vaccines work to boost our immune systems, Dhenni and colleagues argue further research is needed to make any practical recommendations. The new findings may be more relevant to initial boosters given in quick succession, for instance, not necessarily seasonal vaccines that can be given months, if not years, apart, when immune responses on both sides of the body have time to balance out. "This is a fundamental discovery in how the immune system organizes itself to respond better to external threats – nature has come up with this brilliant system and we're just now beginning to understand it," says immunologist Tri Phan. The study was published in Cell. Brisk Walking Could Lower Your Risk of Heart Rhythm Abnormalities A Small Drop in Vaccinations Could Spread Measles to Millions, Study Warns This Severe Brain Disorder Is Common But Often Goes Undiagnosed
India Today
29-04-2025
- Health
- India Today
Left or right arm? Study reveals why location of injecting the vaccine matters
Australian researchers have revealed that receiving a vaccine booster in the same arm as the original dose can trigger a quicker and more effective immune findings of their study, published in the journal Cell, were led by the Garvan Institute of Medical Research and the Kirby Institute at UNSW discovered that specialised immune cells, called macrophages, are 'primed' inside the lymph nodes nearest to the injection site after the first dose. These cells then help position memory B cells - a critical part of the immune system - to respond faster when a second dose is given in the same "This is a fundamental discovery in how the immune system organises itself to respond better to external threats. Nature has come up with this brilliant system and we're just now beginning to understand it," said Tri Phan from the Garvan VACCINE LOCATION MATTERSVaccines work by introducing a harmless form of a virus or bacteria into the body, teaching the immune system to recognise and fight the vaccine is administered, it travels to nearby lymph nodes - the body's immune training hubs. Memory B cells, which help produce antibodies when the body sees the same virus again, are often found in the lymph node closest to where the vaccine was injected. Vaccines work by introducing a harmless form of a virus or bacteria into the body, teaching the immune system to recognise and fight it. (Phot: Getty Images) advertisementUsing advanced imaging tools, researchers at Garvan found that these memory B cells move to the outer areas of the lymph node, where they interact with macrophages already trained by the first the booster is given in the same arm, the 'primed' macrophages quickly react and activate the memory B cells to produce stronger antibodies."Macrophages are known for clearing up infections, but here they're also organising the next immune response," said Rama Dhenni, co-author of the FROM CLINICAL TRIALSTo see if the effect was the same in humans, researchers conducted a study with 30 participants receiving the Pfizer-BioNTech COVID-19 vaccine. Those who got both doses in the same arm had faster and more effective antibody responses, especially in the first week after the second shot."These early antibodies were also better at neutralising variants like Delta and Omicron," said Dr Mee Ling Munier from the Kirby both groups had similar antibody levels by four weeks, scientists say that earlier protection could be critical during outbreaks."This simple strategy, using the same arm, might help build community-level protection faster," said Dr hope the findings will inform future vaccination strategies and possibly reduce the number of boosters needed.
Yahoo
28-04-2025
- Health
- Yahoo
Why using the same arm for vaccines might boost the body's response
When it comes to getting the most out of a vaccine, arm consistency can make a difference. Some studies suggest that getting a booster in the same arm as the initial shot can boost the immune system's response. Now, we're getting clues as to why using the same arm for initial and booster doses might be better for activating the immune system's response to a vaccine. In a small study published April 28 in the journal Cell, researchers from Australia found that when a vaccine is given, specialized immune cells called macrophages prepare to fight inside lymph nodes. The macrophages then direct where memory B cells go to more effectively respond to the booster when it is given in the same arm. According to the team, the findings were made in mice and validated in human participants and offer enough evidence to refine how we approach vaccines. 'A unique and elegant aspect of this study is the team's ability to understand the rapid generation of effective vaccine responses,' Anthony Kelleher, a study co-author and clinician scientist at the Garvan Institute of Medical Research and the Kirby Institute at University of New South Wales Sydney, said in a statement. 'We did this by dissecting the complex biology in mice and then showed similar findings in humans. All this was done at the site of the generation of the vaccine response, the lymph node.' [ Related: New study: US could see millions of measles cases if vaccination rates keep dropping. ] During immunization, a harmless version of a pathogen called a vaccine antigen is introduced into the body. The antigen is then filtered through the lymph nodes. These work like immune system boot camps that train the body to fight off the real pathogen when and if they are confronted with it. Previously, the team from the study looked at memory B cells. These cells are crucial for generating antibody responses when infections return. They found that memory B cells tend to stay on the lymph node closest to the injection site. They migrate to the outer layer of the local lymph node and interact closely with the macrophages–those specialized immune cells primed for battle in the lymph nodes–that reside there. When a booster was given in the same location, those already-on-alert macrophages captured the antigen and activated the memory B cells more efficiently. In turn, this made high quality antibodies. 'Macrophages are known to gobble up pathogens and clear away dead cells, but our research suggests the ones in the lymph nodes closest to the injection site also play a central role in orchestrating an effective vaccine response the next time around. So location does matter,' study co-author and immunologist Rama Dhenni said in a statement. In this new study, the team conducted a clinical study with 30 volunteers receiving the Pfizer-BioNTech COVID-19 mRNA vaccine. Ten of the participants received their booster dose in the same arm as their first dose. The other 10 were given the second shot in the opposite arm. According to the results, the group who received both doses in the same arm began producing neutralizing antibodies against the virus within the first week after the second dose. They also showed to be more effective against the potent Delta and Omicron COVID-19 variants. After four weeks, both groups had similar antibody levels. However, that early protection could be important during an outbreak. 'If you've had your COVID jabs in different arms, don't worry – our research shows that over time the difference in protection diminishes,' study co-author and immunologist Mee Ling Munier said in a statement. 'But during a pandemic, those first weeks of protection could make an enormous difference at a population level. The same-arm strategy could help achieve herd immunity faster – particularly important for rapidly mutating viruses where speed of response matters.' It's important to note that this study included a small sample size and other studies have found benefits in switching arms. In future research, the team hopes to build on this work to refine vaccination guidelines and enhance the effectiveness of vaccines. 'If we can understand how to replicate or enhance the interactions between memory B cells and these macrophages, we may be able to design next-generation vaccines that require fewer boosters,' Tri Phan, a study co-author and clinical immunologist, said in a statement. 'This is a fundamental discovery in how the immune system organises itself to respond better to external threats – nature has come up with this brilliant system and we're just now beginning to understand it.'
