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Mar 8, 2012
In pursuit of a universal flu vaccine
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Flu vaccine being preparedRight around October or November your throat starts to tickle. Then, the sneezing and shivers start. And before you know it you have the flu. As a kid, it’s kind of fun getting to stay home from school and watch TV while your mom makes you soup, but as an adult, getting the flu just means body aches and missed work. We have accepted flu season as an inevitable part of our yearly cycle, right up there with holidays, tax season and birthdays. But that’s only because we haven’t found a way to stop this ubiquitous virus from constantly mutating to avoid our vaccines. 

The FDA has recently approved a new vaccine that protects against four strains of the common flu. That’s one additional layer of protection over last year’s vaccine, the FluMist vaccine offered by AstraZeneca’s MedImmune unit. While last year’s model protected against two strains of influenza A and one of influenza B, this new vaccine fights a second B strain. 

Each year the powers that be make educated guesses about which strains of the flu virus are most likely to affect at-risk populations -- like children, the elderly and those with asthma -- and choose the vaccine strains accordingly. But that means only those strains (four for next year's vaccine) of the virus are covered, while the virus is continually mutating. Thus, the vaccine’s efficacy is limited. Vaccines target hemagglutinin (HA), a protein protruding from the virus’ surface that allow it to attach to and invade host cells. Small mutations in these highly adaptable appendages can create new versions of the virus that often are invulnerable to vaccines designed to fight against the former iterations of the virus -- this is a process called immune escape. 

Thus, while this new quadrivalent vaccine might protect against one more strain during next year’s flu season, the progression of protection and mutation will continue unchecked.  That’s why researchers at Princeton are working to develop a 'universal vaccine' to put a stop to this vicious cycle. The universal vaccine will bypass the HA protrusions and instead target more constant internal proteins in the flu virus that are less likely to evolve.  Under this method, the HAs will still be active, and thus the virus can still infect people, but with less strong results. 

Mass immunization with universal vaccines, maintained over several years, would slow viral evolution in the long term. The vaccines won’t prevent infection, but will reduce the severity of the symptoms, including coughing and sneezing, to cut down on chances of transmitting the virus. In a computational simulation performed by the Princeton team, this practice led to fewer people becoming infected with the flu and thus fewer people gaining immunity to the dominant strain. 

This is the first study to look at the population consequences of the next generation of vaccines, both in terms of epidemiological impact and evolutionary impact on the virus. Current inoculation practices focus on protecting people who are vulnerable to the virus, but this approach does not provide long-term or widespread immunity. Universal vaccines are being developed worldwide, and some have already begun clinical trials. 

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