Researchers have discovered that natural immunity gained from previous flu infections plays a crucial role in the effectiveness of future influenza vaccinations.
A recent study, backed by the National Institutes of Health, conducted by researchers at the University of Georgia, shows that having natural immunity from past flu infections significantly influences how well subsequent influenza vaccines perform.
This could mean that if you are among the roughly 1 in 5 Americans who catch the flu each year, as reported by the NIH, there might be an unexpected benefit from your illness.
Your past infections may help you combat future strains of the virus.
“Overall, the immunity you gain from natural infections boosts your immune responses,” stated Ye Shen, the lead author of the study and a professor in the UGA College of Public Health. “Before this study, we didn’t fully grasp how prior immunity from different flu strains alters the immune responses generated by vaccines. Now, we have a clearer picture of how natural flu immunity affects responses to various vaccines.”
Flu shots are designed to adapt to a changing virus
Each flu season, vaccines are formulated to target specific strains of the virus. Scientists have to predict which strains will likely be circulating beforehand when developing the influenza vaccine.
Despite significant research efforts to create an effective vaccine, it can never be expected to be completely accurate.
The flu virus’s constant evolution and the emergence of new and more aggressive strains complicate treatment efforts.
“In some seasons, the vaccine may not offer adequate protection due to this mismatch,” Shen noted. “This has raised concerns about the vaccine’s efficacy. However, this study reveals the advantages of having preexisting immunity, which is reassuring.”
Vaccination after recovery can enhance immune protection
The team experimented with vaccines derived from various flu strains. Their findings indicated that when animals were infected with one strain, they displayed a stronger immune response when vaccinated with a corresponding strain.
Moreover, overall immunity also improved significantly for animals that received a vaccine targeting a different strain after recovering from the initial infection.
The combination of the body’s natural immune response to one strain and the vaccination that promotes a broader immune reaction to multiple strains offers enhanced protection.
Animals that weren’t previously infected but received the vaccine had a higher likelihood of needing a booster shot because they lacked natural immunity.
This study is part of a larger, seven-year NIH-funded project aimed at developing universal influenza vaccines for at-risk populations.
“Our future research will delve deeper into clinically relevant outcomes, such as actual infections in humans. Merely increasing antibody levels may not be enough,” Shen emphasized. “It’s crucial to understand whether that suffices to defend against the mutations of various influenza strains. This is an important research area addressing individual differences in immune responses.”
This study, published in the journal Vaccine, was co-authored by Yao Lu, who played a key role in data analysis, along with Andreas Handel from the UGA College of Public Health, and Ted Ross from the UGA College of Veterinary Medicine. Additional contributors include Yang Ge, James D. Allen, Tal Einav, Dennis I. Nkaleke, and Fengwei Bai.
