No missing that it is flu season. Like hurricanes in Florida, fires in California, and tornadoes in Oklahoma, either the media reminds us or our friends do.
Massachusetts just declared a flu emergency. The Centers for Disease Control and Prevention (CDC) map showing that there are widespread flu cases in 41 states is on all the news media websites and news reports. And the flu deaths have just surpassed the 1 of 14 deaths threshold to officially be called an epidemic.
There seem to be a lot of people with the flu or flu-like symptoms, which seems strange. The flu vaccine is not something new. It is readily available, far more cheaply than getting the flu is. If you are an hourly worker, it costs the equivalent of 1-2 hours of work, but the flu costs you 8 hours of work.
I think there are four reasons why there is so much flu.
1. Many people do not get the flu shot even when it is available for free, as in many workplaces. There is magical thinking involved. The vaccine is dangerous, they think, or, “it will make me get the flu.” Often there is a fear of needles.
Comparing vaccination rates from November to the previous year, they are about the same: less than 3 out of 8 people. By March of last year, less than 1 out of 2 individuals had been vaccinated. Trends from November to March are likely to be similar this year.
The next two reasons are a bit more complicated.
This table shows the reports of testing of flu strains around the country totaling over 9,000 tests with slightly less than a third positive. There are about 4 times as many Type A as Type B positive tests. Of course, many people with the flu do not get tested. They may call their doctor, who either prescribes an anti-viral or tells them it is too late, that they should drink plenty of liquids, and look for the signs of pneumonia.
So, the next reason is:
2. People contract a virus that is not influenza.
The next image shows tests done at the CDC for different strains. The sample is much smaller, about a seventh of the previous number of positive tests. Note that strains of both Type A and Type B influenza were identified. About a fourth are Type B.
And here are the strains in the 2012-2013 vaccine:
On February 23, 2012 the WHO recommended that the Northern Hemisphere’s 2012-2013 seasonal influenza vaccine be made from the following three vaccine viruses:
an A/California/7/2009 (H1N1)pdm09-like virus;
an A/Victoria/361/2011 (H3N2)-like virus;
a B/Wisconsin/1/2010-like virus (from the B/Yamagata lineage of viruses).
Note the absence of B/Victoria lineage from the vaccine, so the final reason:
3. People contract an influenza virus for which they have not been vaccinated–even though they received this year’s flu vaccine. There has been talk of a vaccine with four strains (quadri-valent) rather than the current three strains (tri-valent), but none yet operational in the US.
4. Even those who get the flu shot do not get perfect immunity. Immunity depends on the weakened or killed virus stimulating the production of antibodies. Everyone’s immune system is different, and those with weaker responses get less protection. Indeed, older folks get a strengthened vaccine now, so that aged immune systems can be stimulated to trigger an adequate response. Also, the antibodies stimulated tend to stay concentrated in the bloodstream, not the lining of the lungs where the virus enters.
Conclusion: The flu virus is inconvenient at best and deadly at worst. You may not get adequate protection from the vaccine, but you get zero protection without it. And get the pneumonia vaccine as well, if you haven’t already: real good chance of a secondary infection if you get the flu and haven’t gotten the pneumonia vaccine.
Comments are closed.