Universal vaccine could put brakes on flu

PRINCETON (US) — A universal vaccine could for the first time effectively prevent wide-scale spread of influenza by shutting down the virus’ ability to spread and mutate.


As reported in the Proceedings of the National Academy of Sciences, the new vaccines would make a bout with influenza less severe, making it more difficult for the virus to spread. At the same time, the vaccines could target relatively unchanging parts of the virus and hamper its ability to evolve and evade immunity.



Controlling the flu, which is now like “chasing a moving target,” could advance from the current reaction stage to that of real population-wide prevention, says lead author Nimalan Arinaminpathy, a postdoctoral research associate who works in the lab of co-author Bryan Grenfell, professor of ecology and evolutionary biology at Princeton University.


“So, at the moment, vaccine programs focus on clinical protection for those receiving the vaccine, but we hope to eventually graduate to being able to control the virus’ spread and even its evolution. Our model provides a strong conceptual basis as to how and why the universal vaccines would achieve that.”

The research presents a realistic and important assessment of how the universal vaccines’ ability to work against a breadth of flu strains can be wielded to benefit public health, says James Lloyd-Smith, assistant professor of ecology and evolutionary biology at the University of California-Los Angeles. Lloyd-Smith had no role in the study, but is familiar with it.


“They give very clear insights about what the impact of these vaccines would be,” he says. “In doing so, this work provides incentive for the vaccine manufacturers to continue this research and development, and it provides some guidance for public health authorities to think about using these new vaccines once they become available.”

The researchers developed their model using an archetype of the universal vaccine. In recent years, outbreaks of potent flu strains—such as avian flu in 2003—and advances in biotechnology have spurred research teams at pharmaceutical companies and government organizations such as the National Institutes of Health to work on cross-protective vaccines. Projections for a publicly available vaccine range from one to five years.

Current flu vaccines are produced to counter the influenza strains that the World Health Organization predicts will dominate a particular flu season. Inoculation typically focuses on protecting people who are vulnerable to the virus. However, this approach does not provide long-term or widespread immunity, Arinaminpathy says. The flu virus is always evolving, and so vaccines need to be updated each year.


Universal vaccines instead bypass the protruding HA surface to target more constant proteins with less evolutionary flair, Arinaminpathy says. Because HAs are still active, the virus may still infect people, but it cannot wreak the same havoc.

The various universal vaccines being developed target different viral components, but they all have the potential to slow viral transmission across many flu variants, Arinaminpathy says. The researchers used that overarching feature in their model vaccine and then simulated the effectiveness of their basic universal vaccine in two types of flu outbreak: pandemic and epidemic.

Raising ‘herd immunity’

A flu pandemic—the sudden and rapid spread of a new, highly contagious strain—is difficult to predict and typically impossible to control through vaccination alone, Arinaminpathy says. But universal vaccines act on virus targets that are relatively constant across all types of flu, even pandemic flu.

The researchers found that the vaccines could be deployed on a large scale to avert a pandemic altogether, even if only a proportion of the population received vaccination. The vaccine would raise “herd immunity,” wherein even unvaccinated individuals are protected because many people around them are immune.


In both cases, mass immunization with universal vaccines, maintained over several years, would slow viral evolution, or immune escape. Significantly, the researchers found that universal vaccines need not be fully protective to control flu. To account for any potential differences universal vaccines might have in the level of flu immunity they provide, it was assumed their hypothetical vaccine would not prevent infection, but only reduce the severity of symptoms such as coughing and sneezing, which would bring down the chances of transmitting the virus.

The researchers’ simulation showed that overall this led to fewer people becoming infected and, thus, fewer people gaining immunity to the dominant flu strain. That would remove the advantage that any new strains might have, Arinaminpathy says. At the same time, lower rates of infection would mean that fewer people could harbor mutant viruses in the first place because they never caught the original strain.

“We found that by putting the brakes on flu transmission, you could also put the brakes on flu evolution,” Arinaminpathy says. “Our model illustrates how we can control the flu this way, instead of simply reacting to it every few years.





Researchers from Duke University, the US Food and Drug Administration, and the National Institutes of Health contributed to the study.

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