This year’s influenza was bad and it’s not over yet.
The stormy seas of January and February for this year’s influenza season has calmed, but by no means is over yet. The nightly television coverage on national news highlighting the magnitude and the severity of influenza cases and has now ebbed to a few messages and it is tempting to conclude that we are out of the woods. To be sure, this season was a very difficult one resulting in rates of influenza cases not seen since 2009 when we were experiencing the pandemic of the H1N1 influenza. Whereas the H1N1 strain of influenza is most dangerous for children and younger adults, this year’s predominant strain, H3N2 is most dangerous for the elderly, though it was dangerous for all ranges of age. The hospitalization data for the elderly skyrocketed as can be seen in the CDC (Centers for Disease Control) information on their web site.
At our pediatric clinic at the University of New Mexico Hospital for the month of January we saw 2,500 patients for urgent care issues, many of whom had influenza or concerns for influenza. Last year for comparison, we saw 1,500 patients in January. At the peak of the influenza season, our Health Science Center had about 400 positive tests for influenza; the most recent information showed 200 positive tests for influenza in the first week of March.
Much has been written about the “failure” of this year’s influenza vaccine to protect from disease. Under usual circumstances, the difficulty with an effective influenza vaccine is anticipating the correct strains of influenza that will by circulating for a flu season. That decision is made by the CDC and WHO (World Health Organization) in February, several months before the flu season even begins. This is necessary because of the time needed to produce the influenza vaccine, especially the vaccine that is made using eggs. For this influenza season, there was no issue with selecting the correct strains for the flu vaccines. The difficulty occurred in the production process of the egg-based influenza vaccine. We know that in nature, the influenza virus in constantly mutating, that is to say the mistakes are made in copying the genetic material of the influenza virus. A very recent research article investigated why the egg-based influenza shot has shown decreased effectiveness over the last handful of years. The researchers showed that for this production method, mutations occurred within the flu vaccine itself which resulted in decreased ability to protect against the influenza H3N2 strain. This development has been very discouraging for all of us in the health care profession and for the public and has contributed to the severe influenza season that we just had. However, reduced effectiveness is NOT to say that there is no effectiveness for the egg-based flu vaccine. In addition, there are other kinds of influenza vaccine that are made from cell-based technology that probably avoids this issue.
So where are we in this year’s influenza season around the 2nd week of March? The delightfully warm weather we have had tempts us to think that we are done with flu. As above, we recorded around 200 cases of influenza recently and there are still many more patients who had influenza that we didn’t test. Each case of influenza is a risk that a severe case may occur. At the peak of influenza season, it was estimated that about 4,000 deaths a week occurred in America due to influenza and complications of the flu. Some of these deaths, tragically, are children. About 1 month ago, our tests showed that the prevailing strain of influenza shifted from influenza A (H3N2) to influenza B and this trend has continued. The quadravalent influenza vaccine (contains 4 strains of flu vaccine) covers this influenza B virus well. Sadly, the high dose influenza vaccine recommended for those over the age of 65 does not cover the circulating strain of influenza B strain.