Understanding the Impact of Natural Flu Infections on Vaccine Effectiveness

Researchers from the University of Georgia discovered in a recent study supported by the National Institutes of Health that the effectiveness of upcoming influenza vaccinations is significantly influenced by the body's innate immunity from prior flu episodes.

This could imply that, if humans are among the unfortunate 1 in 5 Americans who contract the flu annually (as predicted by the NIH), there might be a surprise benefit to the illness.

It might support in battling more advanced viral iterations.

Overall, the preexisting immunity you develop through natural infection helps to strengthen immune responses. We did not 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.”

Ye Shen, Study Corresponding Author and Professor, College of Public Health, University of Georgia

Flu Shots Aim to Keep Up with an Evolving Virus

Each flu season, the flu vaccination targets certain strains of the virus. Thus, when creating the influenza vaccine, researchers must estimate which strains are most likely to become widespread in advance.

Even if the shot is developed after extensive research, it will never be perfect.

It is challenging to combat the flu virus because of its capacity to continuously change and produce new, more aggressive strains.

In some years, we do not 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 is good to know.”

Ye Shen, Study Corresponding Author and Professor, College of Public Health, University of Georgia

Vaccination Post-Recovery can Bolster Immune System

A variety of flu strain vaccinations were examined by the researchers.

Researchers discovered that when given a vaccine that targets the same strain of the flu, animals having an infection from that strain exhibited an enhanced immune response.

However, once the animals were infected with the initial strain of the virus, their general immunity also markedly improved when they received a vaccine targeting a different strain of the virus.

The body was better protected because the vaccine elicited larger immune responses against a range of flu strains, while the body used its natural immunological response to defend itself against one strain.

They lacked natural immunity, animals who received the vaccination but were not initially infected with the virus were more likely to require a booster.

The goal of this seven-year, NIH-funded project is to develop universal influenza vaccines for populations that are particularly susceptible to the disease.

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. 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.”

Ye Shen, Study Corresponding Author and Professor, College of Public Health, University of Georgia