New Four-Strain Flu VaccinePosted: October 1, 2013
Is It Right for You?
Have you heard? There’s a new type of flu vaccine that guards against four strains of flu rather than just the usual three strains.
We have some questions about this new quadrivalent flu vaccine, of course. For instance: Is it safe? How well does it work? (A fair question, considering that last year’s vaccine was only 56% effective.) How can you tell whether it’s right for you? And will you be able to find it if you want it? (Another fair question, given last year’s shortages.)
We’ve got these answers and more…
There are two main types of influenza viruses, influenza A and influenza B. According to the Centers for Disease Control and Prevention (CDC), influenza A viruses are divided into two subtypes based on their surface proteins, and each subtype is further broken down into various different strains. Influenza B viruses are not divided into subtypes but are broken down into two main strains. More than one strain of influenza virus may be circulating at any given time…and different strains may appear at different times throughout a particular flu season.
When vaccines are being developed for an upcoming flu season—which occurs about six to nine months in advance—researchers do their best to predict which of the various possible strains will be circulating. Making this job even tougher is the fact that flu viruses continually change over time, producing new strains that the body’s immune system doesn’t recognize. The type-B virus changes gradually, a process called antigenic drift. With type A, the changes can be gradual…or they can be abrupt and major, a process called antigenic shift.
The traditional flu vaccine offers protection against two influenza A strains (one from each subtype) and one influenza B strain. But influenza strains are different enough from one another that immunization against one strain offers only very limited protection against other strains. As improved viral diagnostics have shown the importance of protecting against the second B strain, researchers have been working to develop a quadrivalent vaccine that provides protection against both of the two main influenza B strains. Finally this four-strain flu vaccine has gained FDA approval and, this year, it is available for the first time.
Problem: Until vaccine manufacturers get fully up to speed with the new quadrivalent manufacturing process, most vaccines out in the market will be the traditional trivalent (three-strain) variety. According to the CDC, of the estimated 135 million doses of flu vaccine that manufacturers will produce for use in the US this flu season, about 30 million to 32 million will be quadrivalent—the rest will be trivalent. It will take about three years before all flu vaccines offer four-way protection.
In addition to concerns about availability, the new four-strain vaccine also raises questions—about its effectiveness, risks, cost, etc. For answers, Daily Health News turned to William Schaffner, MD, professor of preventive medicine at Vanderbilt University School of Medicine and past president of the National Foundation for Infectious Diseases. Here’s what Dr. Schaffner had to say about vaccine options for the coming flu season.
How much more protective is the quadrivalent vaccine compared with the traditional trivalent vaccine?
From a public health perspective, the impact of adding the fourth “arm” to the flu vaccine may prove to be modest or quite significant. It will depend on the available supply of the quadrivalent vaccine (which may be limited)…the number of people who opt for it…and whether that fourth strain ends up being a dominant force in the upcoming season’s circulating “flu virus stew.” For your personal health, though, that fourth arm of protection can make a huge difference if the main circulating strain ends up being the one that’s not included in the trivalent vaccine. We won’t know whether that’s the case until flu season is underway.
Is the quadrivalent vaccine any riskier than the trivalent vaccine?
No. Side effects are comparable for both the trivalent and quadrivalent vaccine. Possible side effects include redness at the injection site…nasal congestion from the nasal spray version of the vaccine…or, very rarely, a low-grade fever.
Who should get the quadrivalent vaccine?
In an ideal world, everyone who wanted it would get the quadrivalent vaccine this year—but that’s not possible because manufacturers can’t yet produce enough to meet the full demand. Your best bet: Contact several local vaccine providers—your doctor, pharmacy, community or worksite flu shot clinic—and ask whether they have the quadrivalent vaccine. When you find it, get it without delay before they run out.
But what if no one in your area has the quadrivalent vaccine now or expects to get it within a few weeks? Then go wherever you usually go for your flu vaccination and get whatever type they do have. Don’t keep holding out for months for the four-strain vaccine—because you very well might wind up catching the flu before you have a chance to get vaccinated.
What is the difference this year between the flu shot and the nasal spray vaccine?
The nasal spray, called FluMist, contains a live attenuated (weakened) form of the virus. It is recommended only for healthy people ages two through 49. This year, the nasal spray vaccine is exclusively available as a quadrivalent vaccine. Babies, people age 50 and up, pregnant women, people with asthma or other respiratory problems, and caregivers of severely ill patients who require a protective environment should instead get the vaccine that contains the inactivated virus, which comes in the form of the injected vaccine. Most flu shots this year have the trivalent vaccine, but some quadrivalent shots will be available.
Why do some people get sick after being immunized?
Let’s put a myth to rest. You cannot get the flu from the vaccine because the virus has been killed or attenuated. It takes about two weeks to build up immunity after getting the vaccine—so if you happen to develop the flu shortly after being vaccinated, it’s not from the vaccine—it’s because you were exposed to the disease before your immune system had a chance to get fully armed.
There is also a high-dose flu vaccine this year. How well does it work?
The high-dose flu shot is a trivalent vaccine licensed for use in adults ages 65 and older—the population most at risk of dying from influenza. It has been available for two years, but researchers didn’t know whether it actually offered improved protection. Now we do know. In a study of 30,000 people age 65 and up who were randomly assigned to either the regular-dose trivalent vaccine or the high-dose trivalent vaccine, the high-dose vaccine was 24% more effective in preventing flu. There should be plenty of high-dose vaccine available this year.
For someone 65 or older, what’s the better choice—the high-dose trivalent vaccine or the regular-dose quadrivalent vaccine?
There’s no clear answer to that question because we don’t yet have the data for a head-to-head comparison. Both are good options—so take whichever one is available when you go to get your vaccination.
How do the various vaccine options compare in terms of cost?
The quadrivalent vaccine and the high-dose vaccine cost a little more, but they are covered by insurance just as the traditional trivalent vaccine is. If you don’t have insurance, your cost will vary depending on where you get vaccinated and the specific type of vaccine, but you can expect to pay between $30 and $85—real bargains compared with the potential costs of your care and lost productivity (not to mention your misery) if you actually get the flu.
Helpful: For locations near you where flu vaccines are administered, visit http://flushot.healthmap.org.
Source: William Schaffner MD, professor of preventive medicine, Vanderbilt University School of Medicine, Nashville. Dr. Schaffner also is an associate editor of Journal of Infectious Diseases, past president of the National Foundation for Infectious Diseases and winner of numerous research awards.
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