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Athens, GA – A recent study funded by the National Institutes of Health (NIH) has unveiled a potentially significant benefit of experiencing influenza infections: enhanced immunity following vaccination. Researchers from the University of Georgia (UGA) found that natural immunity developed from previous flu infections can substantially impact the effectiveness of future influenza vaccinations.
According to the NIH, approximately 1 in 5 Americans contract the flu each year. For these individuals, the study suggests an unexpected upside to their illness: it may help improve their ability to combat future versions of the virus. “Overall, the preexisting immunity you develop through natural infection helps to strengthen immune responses,” said Ye Shen, the study’s corresponding author and a professor in the UGA College of Public Health. “We didn’t fully understand how preexisting immunity through natural infection with different influenza strains changes vaccine-elicited immune responses before this study. Now we have a better understanding of how preexisting immunity to influenza influences immune responses to different types of vaccines.”
Navigating the Evolving Virus
Flu vaccinations are designed to target specific strains of the virus each flu season. Scientists must make educated predictions regarding which strains are likely to be circulating, a task that is complicated by the virus’s ability to evolve and develop new, virulent strains. Shen noted, “In some years, we don’t have very good protection from the vaccine because of that mismatch. People have started to worry about whether the shot is actually protecting them from the flu because of that. With this study, though, we do see benefits of having preexisting immunity, and that’s good to know.”
Immunity Boost through Vaccination
The research involved testing vaccines made from various flu strains. The findings revealed that when animals were infected with one strain of the flu, their immune response was significantly heightened when they were subsequently vaccinated with a vaccine targeting the same strain. Interestingly, the study also demonstrated that overall immunity improved when the animals received a vaccine targeting a different flu strain after being infected with the original strain.
This dual approach allows the body to protect itself against one strain through its natural immune response while the vaccine elicits broader immune responses to a spectrum of flu strains. Conversely, animals that were not initially infected and only received the vaccine were more likely to require a booster shot due to a lack of natural immunity.
Looking Ahead
This study is part of a larger, seven-year NIH-funded project aimed at developing universal influenza vaccines for vulnerable populations. “Our future studies will further explore more clinically relevant outcomes, including actual infections in humans. It may not be enough just to push your antibodies higher,” Shen remarked. “Is that enough to protect you from mutations of different influenza strains? This is where individual-level heterogeneity becomes important, which remains an ongoing area of research in the field.”
Published in the journal Vaccine, the study also included contributions from co-authors Yao Lu, who conducted much of the data analysis, Andreas Handel from the UGA College of Public Health, and Ted Ross from the UGA College of Veterinary Medicine. Other contributors included Yang Ge, James D. Allen, Tal Einav, Dennis I. Nkaleke, and Fengwei Bai.
This research underscores the importance of understanding how natural infections can play a crucial role in enhancing vaccine responses, ultimately paving the way for more effective flu prevention strategies in the future.
