Last week we received our first report on the 2014-2015 influenza season already in progress.
- From all the tests reported to the CDC so far this year, 91% were from influenza A virus, and 9% were from influenza B virus.
- Almost all of the influenza A virus was the H3N2 strain.
- 52% of these H3N2 strains were antigenically different than the H3N2 strains included in this year’s flu vaccine.
What this means is that since the World Health Organization selected the viruses to be covered in this year’s vaccine back in February, the H3N2 virus has mutated, or “drifted” from the original. It’s not that WHO didn’t make the right choice for the components of the vaccine; it’s that the virus evolved, making the current flu vaccine less effective against the predominant influenza strain. Even if the flu vaccine is not as effective as hoped, Jessica Firger says it’s not worthless:
How big a difference will this make? CBS News chief medical correspondent Dr. Jon LaPook says this year’s vaccine will probably be about a third less effective than usual. “In a typical year, the flu vaccine is effective at reducing illnesses caused by the flu by about 60 percent. It’s not 100 percent, it’s about 60 percent,” he explained. “In previous years when there’s been a similar mismatch to what we’re seeing this year, the effectiveness goes down to about 40 percent.”
However, he says even though the vaccine is not perfect, people should still get a flu shot. “Even if it’s 40 percent effective, it’s better than nothing.”
CDC director Tom Frieden agrees that a drifted influenza strain doesn’t minimize the importance of getting a flu vaccine. On the contrary:
Frieden still recommended that US citizens receive the current influenza vaccine for protection against the other included strains.
“If we have a severe season with H3N2 virus predominating, getting a vaccine — even if it doesn’t provide as good of protection as we would hope — would be more important than ever, and remains the single-most effective way to protect yourself against the flu,” Frieden said.
Alyson Wyckoff reports this sobering news:
Five flu-related pediatric deaths have been reported so far this season; four were attributed to influenza A, and one to influenza B. It is not known whether the four deaths linked to influenza A were due to the drifted strains, the CDC said. In past years, 90% of pediatric deaths occurred in unvaccinated children.
“This highlights how unpredictable the influenza virus is from year to year,” said Henry H. Bernstein, D.O., M.H.C.M., FAAP, Red Book Online associate editor and an ex officio member of the AAP Committee on Infectious Diseases. “Even though there appears to be a drifted strain, it is still critically important to get vaccinated. Now is as good a time as any,” he said.
There are two antiviral medications approved in the U.S. for treating influenza — oral oseltamivir (Tamiflu) and inhaled zanamivir (Relenza) — but getting a prescription isn’t as straight-forward as it might seem. For the most part, pediatricians prescribe antivirals only for children who are at high risk of developing severe disease symptoms and complications such as children under the age of 2 and children with chronic medical conditions. It’s important to note that antiviral medications need to be started within the first 48 hours of beginning symptoms to be effective and even then, they only shorten the course of illness by a day or so. In addition, finding sufficient supplies of these antiviral medications in pharmacies has proven challenging over the last few years.
The best practice when it comes to influenza is prevention with this triad of strategies:
- Proper and frequent hand washing.
- Isolation from others when you get sick (i.e. stay home!).
- Get the flu vaccine every year.