Better flu vaccine on the horizon
During the heat of summer, people tend to forget about the flu. Yet as high temperatures begin to decline, we’re reminded that influenza, a serious disease that can lead to hospitalization and even death, will soon return.
For the past several months, pharmaceutical companies and U.S. public health officials have been busy making and planning for the distribution of millions of doses of the flu vaccine to protect Americans in the upcoming season. The American Academy of Pediatrics released a new recommendation this week that all children ages 6 months or older be immunized against influenza as soon as the vaccine is available.
Getting vaccinated each year remains the best way to protect yourself against the seasonal flu and lessen the chance you will spread the infection to others.
Despite these efforts, each year between 3,000 and 49,000 people in the United States and approximately 500,000 worldwide die from the flu and its complications. Seasonal flu vaccines reduce the risk of illness in those vaccinated by about 60%, according to the Centers for Disease Control and Prevention. Clearly, we need new improved influenza vaccines to provide an even a better level of protection.
The problem is that for decades the technologies used to make flu vaccines have remained static. This fact, coupled with the intrinsic nature of these viruses to change, has created an untenable situation.
Year-round, scientists, vaccine manufacturers, and public health officials scramble to protect the public against both seasonal and potential pandemic influenza threats, the latter illustrated most recently by the H7N9 bird flu infections in humans occurring in China.
Flu viruses are monitored continually to identify those most likely to cause human illness. But it takes at least six months to produce an influenza vaccine once the targets have been identified; by late February public health officials must choose three or four virus strains expected to be circulating widely the following season.
It’s a time-consuming and cumbersome process. These strains usually are grown in eggs (or more recently, in cells), inactivated and then incorporated into next season’s flu vaccines.
A major drawback of this strategy is that the circulating flu viruses can evolve significantly while the vaccine is being prepared and deployed, leaving us with a less effective vaccine for the threat at hand. And always looming is the specter of a novel flu virus emerging to which humans have little or no immunity, potentially triggering an influenza pandemic — as happened in 1918, and again in 1957, 1968 and 2009.
Among the two dozen vaccine-preventable diseases, including measles, mumps, polio, smallpox and hepatitis, seasonal influenza is the only one for which a new vaccine is recommended every year. A more efficient approach is long overdue.
The medical research community has set its sights on developing a revolutionary type of flu vaccine, one to protect against a broad spectrum of flu viruses — a so-called universal influenza vaccine. Experiments in animals and early phase clinical trials in humans indicate that this concept of broad protection is entirely feasible.
Traditional flu vaccines target regions in the head of a protein found on the surface of the virus, regions readily seen by the immune system but prone to mutations as the viruses carelessly reproduce themselves. In contrast, the new vaccine may target more stable regions of the influenza protein found in the stem, somewhat hidden from the immune system by other molecules nearby, that rarely vary from virus to virus.
Optimally, a universal flu vaccine would protect against both seasonal and potential pandemic flu viruses and provide long-lasting protection so it would be given just once or in a series of boosts, like the measles vaccine.
Realistically, however, a universal flu vaccine likely will be developed in incremental steps rather than in one giant leap — a flu vaccine given once every ten years, like a tetanus shot, for example, or one shot that offers cross-protection against a subgroup of related influenza viruses is more likely in the short term.
A universal flu vaccine would modernize our prevention strategy, lower health care costs, and bring influenza vaccines more in line with other licensed vaccines.
Much work needs to be done before this goal is reached, and in the meantime, getting an annual flu shot in its current form is still the best protection for everyone. But in 2013, 80 years after scientists discovered that influenza is caused by a virus, we all can be encouraged that research on a transformative approach to influenza prevention is moving ahead.
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