An Unexpected Space Discovery May Improve Vaccines for Older Adults

Some of the most exciting science happens when an experiment doesn’t reveal what you thought it would. When the data you collect supports your hypothesis, it confirms what you already suspected. But when the data surprises you, it can open a door you didn’t even know was there.

For a team of researchers at the global pharmaceutical company Sanofi, unexpected findings from research on the International Space Station (ISSInternational Space Station) may help scientists develop more effective vaccines, particularly in a key population: older adults.

“MicrogravityThe condition of perceived weightlessness created when an object is in free fall, for example when an object is in orbital motion. Microgravity alters many observable phenomena within the physical and life sciences, allowing scientists to study things in ways not possible on Earth. The International Space Station provides access to a persistent microgravity environment. provides a unique, unexplored variable that few biopharmaceutical researchers have leveraged or considered,” said Brian Schanen, Sanofi’s global head of biomarkers. “What it could bring to our research and next-generation products is incredibly exciting, but you have to think a little orthogonally for that to occur, and it takes leadership that’s willing to embrace that mindset and take those leaps.”

As we age, our immune system declines, and Schanen and his colleagues are trying to understand why. But studying immune aging is difficult because it unfolds over decades. To address this issue, the team was looking for a way to rapidly age young immune cells, and space research caught their attention.

Breaking Through Immune Baggage

Unlocking better vaccines requires overcoming a fundamental tenet of immunology: your immune system’s effectiveness against future biological threats is shaped by past experiences. Did you know that your first flu infection left a lasting imprint on your immune system? It’s true—that initial infection strongly influences how the immune system recognizes and responds to influenza infections later in life.

When you come into contact with a virus, your immune system is activated to fight the threat. It develops antibodies that will recognize the virus in the future to quickly neutralize it. Vaccines work in a similar way. They contain parts of a virus that allow your immune system to develop antibodies to the virus without making you sick. Whether by exposure to a virus or to parts of the virus in a vaccine, the body builds immunity to what it encounters.

How do you break through? One way is to use adjuvants. Derived from a Latin word meaning “to aid,” adjuvants help grab the immune system’s attention and steer it toward a productive response. As people age, however, some immune pathways become harder to activate. This helps explain why older adults often do not respond as well to vaccines. If researchers could uncover the fundamental drivers of immune aging, also known as immunosenescence, they may be able to design adjuvants that work around them.

The problem is that immune cells from people in their sixties and seventies carry decades of immune baggage—from childhood illnesses to viruses encountered in adulthood and everything in between. This clouds the picture and makes it hard to identify the pathways tied to immune aging. To overcome this challenge, the researchers turned to space.

“If putting young immune cells in microgravity can induce key functional features associated with immunosenescence, it could allow us to study age-related immune dysfunction in an accelerated way,” Schanen said. This would allow researchers to study immune aging without all the baggage.

The Bold Move to Space

In 2021, Sanofi’s project launched to the ISS on NASA’s SpaceX Crew-2 mission. “It was the nexus between biology from the laboratory and the raw engineering of a rocket,” Schanen said. “There are few times in your scientific career that you get the hair standing up on the back of your neck, but everyone watching the launch had that sensation.”

For their experiment, the team isolated immune cells in blood samples collected from two groups: 12 young adults (ages 19-35) and 12 older adults (ages 65-79). To adapt their research for the microgravity environment, the team partnered with ISS National Lab Commercial Service ProviderImplementation Partners that own and operate commercial facilities for the support of research on the ISS or are developing future facilities. BioServe Space Technologies.

“We use cytokines as a readout to understand what direction the cells are headed to see if it’s a productive response,” Schanen said. Through decades of research, scientists have identified roughly 50 cytokines that help interpret immune behavior, but the story is far from simple. “It’s quite complicated and still very much an active area of study, trying to understand what some of these complicated signatures mean.”

Although examining cytokines is useful, it provides only a partial view, and cytokines alone do not fully predict the durability of immunity, Schanen explained. Another issue is timing. Cytokines are produced continuously, but researchers can only measure them at specific sampling points that serve as snapshots. To capture a more complete view, scientists use RNA sequencing. This method provides a detailed map of gene activity, revealing which genes are over- or under-expressed during an immune response.

To collect samples for analysis, the astronauts carefully moved the cells from the incubator to the Life Sciences Glovebox on the ISS. Countryman recalls the suspense of waiting to see the cells.

“We did a lot of work to successfully implement the experiment, but you never really know until you see it,” she said. When the plate came into view—displaying bright shades of red, orange, and yellow—it was clear the cells were alive and metabolizing nutrients. “Seeing those colors, we knew the cells were growing, and that was incredibly exciting.”

A Surprising Twist

Sanofi’s bold decision to take its research to space paid off in an unexpected way. When the team analyzed the cells from the ISS, they were shocked. Instead of seeing the steady immune decline they expected, they found just the opposite—microgravity triggered a strong boost in immune function.

Even more striking, Schanen says, was that the immune cells were activated before any treatments were added. “It was startling that just going to space and being in microgravity had an effect on the cells. This early activation may reflect a stress response induced by spaceflight.”

After introducing stimulants and adjuvants, the response was even more pronounced. Cytokine analysis revealed a markedly stronger pro-inflammatory response in the spaceflight cells, which was confirmed by RNA sequencing. This is key because controlled inflammatory signaling plays a critical role in activating the adaptive immune system, which establishes durable immunity.

“Again, this wasn’t expected because we thought that being in space would suppress immune function,” Schanen said. “Instead, we had microgravity leading us down a path where there’s the potential to boost a pro-inflammatory response.”

“Observing this early immune spike and identifying pathways that are highly reactive and more universal between younger and older cells could be valuable from a drug development perspective,” Schanen said. “If microgravity gives us a place to study immune function differently, it could lead to important future directions, not just for us but the industry in general.”

Based on these results, the team formed a new hypothesis: the stress of microgravity may initially trigger a heightened immune response that, if sustained, could contribute to cellular exhaustion-like states that resemble aspects of immunosenescence.

Enabling researchers to explore the unknown—where unexpected results can lead to breakthroughs—is what it’s all about, Countryman said. “We fly experiments to reveal effects you can’t see on Earth so teams can learn something new or find something surprising.”