Flu Vaccine Still Important, Despite ‘Drift’ of This Season’s Dominant Strain

By: Allison Hydzik

It sounds counter-intuitive, but the recent U.S. Centers for Disease Control and Prevention (CDC) announcement that this season’s dominant flu strain may not be a good match to the influenza vaccine is even more reason to get the flu shot, UPMC doctors say.

And this week – coincidentally National Influenza Vaccination Week – is prime time for those who haven’t rolled up their sleeves to get immunized, since it’s shaping up to be an early flu season.

84469732“I have two messages for the public – if you’re not vaccinated, now is the time because we’re seeing a spike in flu cases, and the flu is definitely circulating in Western Pennsylvania. And if you have symptoms of flu, particularly if you have heart disease, a lung condition or are otherwise vulnerable, get in touch with your doctor to get an antiviral medication,” said Richard K. Zimmerman, M.D., M.P.H., a professor in Pitt’s Department of Family Medicine  who researches influenza vaccine effectiveness.

World health officials select the strains of flu for the seasonal flu vaccine nearly a year in advance of the coming flu season in order to give vaccine manufacturers time to produce it. This summer, one of the strains – H3N2 – “drifted,” meaning it is now different enough that the vaccine is not very effective against it.

The CDC is recommending that people who are particularly vulnerable to getting very sick from the flu – such as the elderly and people with lung conditions or otherwise compromised immune systems – see a doctor to get antiviral medication at the first signs of flu-like illness. Flu symptoms include fever, cough, congestion, headache and body aches. The antivirals Tamiflu and Relenza can lessen flu symptoms and shorten the duration of the illness if taken shortly after symptoms appear.

About half of the flu cases that doctors are seeing early this season are of the drifted variety.

“But the other half are still very well-covered by the vaccine,” said David A. Nace, M.D., M.P.H., director of long-term care and flu programs in Pitt’s Division of Geriatric Medicine and chief medical officer for UPMC Senior Communities. “And it is possible that the shot offers some coverage for the drifted strain as well.”

Allegheny County has 105 confirmed cases of the flu, according to the Pennsylvania Department of Health. Nearly every case confirmed in UPMC labs has been the H3N2 strain, though it isn’t clear yet if they are of the drifted type. UPMC has already had pediatric and adult hospitalizations due to the flu.

Dr. Nace said that the more people who are vaccinated, the more difficult it is for the flu to circulate. This can help keep those who are most vulnerable to the flu from contracting the virus. The H3N2 strain is worrisome because it typically results in higher mortality, particularly among young children and the elderly.

When the vaccine isn’t a perfect match for the flu strain that is circulating, it is even more important to take added precautions, such as coughing or sneezing into your elbow, washing your hands frequently, staying home when sick and not visiting hospital patients or people who are particularly vulnerable to the flu when you have flu-like symptoms.