Yes, it’s that time of year: time to get vaccinated for influenza. Influenza has been reported north of Denver this week. It is hard to predict at this time if we will have an early start to this year’s influenza season. Influenza cases typically increase in January, but can be as early as November or as late as March.
The good news is that Pediatric Associates of Northern Colorado has the 2016 – 2017 influenza vaccine and we are scheduling patients with most insurances for our Flu Shot Clinics. (We still await vaccine delivery from the Vaccines for Children Program for our Medicaid, Self Pay and Health First Colorado patients. Email for more information.) We will not be offering the nasal Flumist vaccine this year. See the below link for the CDC guidelines and why they do not recommend it.
I’m always the first in line to get my flu shot, but it has generally been one of Medicine’s least popular vaccines. This is too bad since the vast majority of all vaccine preventable disease complications in the United States arise from influenza and the cost of a severe epidemic has been estimated to be about $12 billion in lost work hours, hospitalization costs, elder and child care expenses and who knows how much in not very helpful over the counter cold medicines.

Influenza Incidence
An average of more than 200,000 hospitalizations per year are related to influenza, with about 37% occurring in persons younger than 65 years. In nursing homes, attack rates may be as high as 60%, with fatality rates as high as 30%. Among children 0–4 years of age, hospitalization rates have varied from 100 per 100,000 healthy children to as high as 500 per 100,000 for children with underlying medical conditions. Hospitalization rates for children 24 months of age and younger are comparable to rates for persons 65 and older. Children 24-59 months of age are at less risk of hospitalization from influenza than are younger children, but are still at increased risk for influenza-associated clinic and emergency department visits.

This puts influenza in the top 10 reasons for pediatric admissions to hospitals:
1. Pneumonia
2. Asthma
3. Acute bronchitis
4. Mood disorders
5. Appendicitis
6. Dehydration
7. Skin and subcutaneous tissue infections
8. Epilepsy
9. Urinary tract infections
10. Influenza
I say “puts it in the top ten”, but of course many pneumonias, asthma attacks, and bronchiolitis cases arise from influenza, too, so the real incidence could be higher if one of these were listed as the principle diagnosis in place of influenza.
So, why is this very useful vaccine so unpopular to some? Some people, including many dear to me, believe that the flu shot has given them “the flu” in the past. Right off the bat, I want to say that in the flu shot, there is no living flu virus. Just sugar and protein virus components of one of the many influenza strains, combined with the usual types of vaccine solution immune stimulators. (
Now that I’m on base, I’d like to say that some people DO feel lousy for a day or two after getting the flu shot. That’s different than in infection and is related to the mechanism by which vaccines provide immunity.

How does the vaccine work?
The way that vaccines work is to fool your immune system into believing it is fighting an infection with the particular virus for which the vaccine was invented. When you get the flu shot, your immune system kicks into gear and releases all those chemical calls-to-arms that we rely upon to fight disease whenever it occurs. The difference is that after 1 -2 days, the immune system calls off the attack and declares a false alarm. It has now prepped itself for the real thing should the virus come in to the respiratory tract when your colleague sneezes on you in the office; or a classmate sneezes on your kid at school.

Yeah, but I really did get sick for two weeks after that flu shot 3 years ago.
To understand this, one must realize that besides influenza, the late fall through mid-spring months are packed end-to-end with virus after virus: enteroviruses, coronaviruses, rhinoviruses, respiratory syncytial viruses, parainfluenza viruses — all in multiple circulating strains. At any given time, each of us is getting hit with a few of these a week during the winter months. Sometimes we bump into one that we are not equipped to fight off quickly.
For many of these viruses, though, we adults do have lasting immunity. We’ve seen this virus or something pretty close to it before and so, the virus causes fewer problems for us than influenza for which we do not form long lasting immunity.
Unfortunately, our kids in school or daycare those first few years catch virus after virus because it is their first time seeing many of these. After a few years, they, too, have a well-schooled immune system and don’t get sick as often.

I got the flu shot, but still got the flu.
Sometimes the flu vaccine doesn’t work and we catch influenza, despite having received a vaccine. There are a couple of reasons for that. First off, sometimes the scientists working on that year’s flu vaccine incorrectly estimate which strains of the virus will be most prevalent in North America that year. (More on that in a minute because it is really interesting.)
Another reason that the flu shot may not keep us from catching the flu is that a particular flu virus strain might be your or my “silver bullet.” Our immune system has no talent for fighting it. Another scenario is that we may be like Superman around Kryptonite at that moment.
What I mean in the first case, is that the nuances of our own innate immunity have caused the vaccine to be poorly immunogenic. We just don’t “see” this virus as a threat and fail to form antibodies against it.
Tricky stuff. A lot of scientists are looking at these types of questions.

What about the intra-nasal flu vaccine?
There has been another form of flu vaccine the last few years. FluMist contained an “attenuated” live flu virus which was administered intranasally. An analysis of the data on FluMist vaccine effectiveness for the last three years showed that only about 3% of recipients developed immunity to one of the flu strains contained in the vaccine (H1N1). For this reason, the manufacturer will not bring a product to market this year and instead return to the lab to try to figure out how to rejigger the vaccine to provide immunity to those who have difficulty with an injectable vaccine.

OK, last but not least: Why do we need to get a new flu shot every year?
It turns out that the parts on the surface of the virus (antigens) that identify the virus as foreign to our bodies change frequently. Our immune system has to make new antibodies every year specific to the strains of flu virus it sees that year.
No lasting immunity, unlike all those other childhood immunizations.
There are two major antigens we talk about that identify the virus: H (hemagglutanin) and N (neuraminidase). There are at least 18 kinds of H and 9 kids of N. How do they know which strains to put in? The CDC receives influenza viruses from all over the world and tests these to see if they are similar or different to what was in last year’s vaccine. When they see a new variant of the virus, they look at the spread of that virus in China and other East Asian countries. If it seems to be spreading quickly in people there, they test it against the serum of volunteers in the US who get their flu shots without fail every year. If these folks don’t have antibodies that are effective against the virus, the new strain is added to that year’s seasonal vaccine.
Pretty cool, right? Big government science and your tax dollars at work. In my opinion, money well spent.

Please call our office if you have any questions about influenza or the flu vaccine.
Dr. Michael Hobaugh