Monday, October 22, 2012

Flu shot anyone?

The flu vaccine.  What do we need to know to decide if we want to get it for ourselves and for our kids?  I am going to be honest.  This is a difficult post to write.  There are strong emotions associated with vaccinating and not vaccinating our children.  

Children, even healthy children, can die from the flu.  How many die each is year varies with the circulating virus and the severity of the flu season.  The worse season was the 1918-1919 pandemic when more than 20 million people died. 
Some day I should write an "Immune System 101" post.  But here is a quick description.  The immune system has two kinds of "troops" for fighting a virus or a bacteria.  It had general or non-specific troops and it has specialized or specific troops.  The general troops are the first responders.  They catch a virus.  If the body has seen it before it usually will have specialized troops that are more efficient at killing the virus.  If it has these specialized troops, the immune system will send them out and quickly make more for the fight.  If you have enough of these troops you don't get sick.

If you don't have specialized troops, you body develops them so it can fight the virus.  But this takes time and the general troops may not be able to keep up.  That is when you get sick. 

Usually, adults' immune systems have seen a flu virus and have some specialized troops available to attack a flu virus, but in the 1918 virus "looked" different enough that for most people specific immune system did not recognize it .  And that is why so many people died that season.

You have heard the phrase use it lose it?  That applies to your specialized troops.  If your body doesn't ever use the specialized troops for flu, it may stop making them.  So based on all of this information about the flu, it is thought that by getting the vaccine each year, people will not only be able to avoid getting the flu this year, but the immune system may become better at recognizing it.  Possibly even strains that are not in the vaccine. 

Worst Case Scenario

So, to basically make an informed decision about the flu shot, we need to have an idea of what is most likely to happen if you or your child gets the flu and look at the worst case scenario.  I discuss this more here.  But depending on your child’s health and age, most likely he would be sick for a week or two with fever, cough, runny nose, and sneezing.  He could get an ear infection, pneumonia, or other complication. He could be hospitalized.  You could be hospitalized if you catch it as well.  Worst case scenario is death. But the risk of catching the flu depends on your environment.  

I have a relatively high risk of catching the flu as a healthcare provider seeing sick kids during flu season with my own children attending public school.  Someone else who works from home and homeschools their children is going to have much less exposure to the flu virus.
The h1n1 Swine Flu virus vaccine shot for Emilio. Side effect symptoms: "Squeal like a Pig" by Dj Crazy Gabe
The h1n1 Swine Flu virus vaccine shot for Emilio. Side effect symptoms: "Squeal like a Pig", a photo by Dj Crazy Gabe on Flickr



We also need to know how effective the vaccine is and what all the possible consequences or side effects of the shot are.   From my review of the literature there is not a clear answer to how effective the vaccine will be.  This is because effectiveness changes each year depending on the circulating virus and the match of the vaccine.  And it depends on how old the people receiving the vaccine are and whether they get the TIV or LAIV.

Oops, I just threw some abbreviations at you.  Let me explain.  The TIV stands for the trivalent (or three strain) inactivated (killed) vaccine.  LAIV stands for live attenuated influenza vaccine.  It is a nasal spray.  The only live flu virus that is FDA approved in the United States is FluMist. According to the CDC,
“the nasal spray flu vaccine does contain live viruses. However, the viruses are attenuated (weakened) and cannot cause flu illness. The weakened viruses are cold-adapted, which means they are designed to only cause infection at the cooler temperatures found within the nose. The viruses cannot infect the lungs or other areas where warmer temperatures exist”.
Back to effectiveness.  Overall, the flu shot is effective approximately 50-70% of the time.  Meaning, your immune system responds to the vaccine enough to protect you from the virus slightly better than half of the time.  The flu shot effectiveness is higher for kids under 6, and slightly better for FluMist in this age group.  The injection seems slightly better for healthy adults.  And there is not enough evidence for effectiveness in adults over age 65.  Actually, in reading the evidence, numbers seemed to vary greatly.  In fact, some meta-analyses showed the effectiveness at less than 50% for healthy adults.  And many of the studies are funded by the pharmaceutical company who manufactures it.  I agree with the call for more publicly funded (not potentially biased) studies at each age group.  I will list links to the research I looked at following the post.

Reactions and Side-Effects

OK, on to reactions to the vaccine.  All the vaccines are made with eggs, so an allergy could cause an allergic reaction to the vaccine. "Although," according to Children's Hospital of Philadelphia (CHOP),
"the influenza vaccine is made in eggs and some people are severely allergic to eggs, the quantity of egg proteins in the vaccine is insufficient to cause a severe allergic response. But just to be sure, people with severe egg allergies should remain at their provider's office for about 30 minutes after receiving the influenza vaccine."
There may be an extremely small chance of experiencing Guillain-Barre syndrome after immunization, but this has not been shown in current studies. Most people have soreness at the injection site if they receive a shot.  People who get FluMist could have cold symptoms: runny nose, fever, fatigue, aches, chills, or sore throat. There is no evidence of death as an adverse reaction to the flu shot or FluMist.  However, according to the recent Lancet article more research is necessary on "potential harms".

Recently, the CDC has been investigating whether there is an increased risk for seizures following a influenza shot.  It appears that in children under 5 who also receive a Prevnar shot on the same day, there may be an increased risk for febrile seizure.

Many people also consider the preservative and other components in the vaccine.  Thimerosal (mercury-based) is used as a preservative in some flu shots and is left over from the process of creating the flu vaccine in other shots.   If the flu is in a multi-dose vial, it will have a preservative in it.  If it is in a single dose it usually does not have Thimerosal.  Fluvirin single dose has trace amounts  .FluMist is always prepared as a single use and does not have a preservative in it. To see which vaccines have Thimerosal look here and to learn more about it look here.  By the way none of the the flu vaccines have aluminum in them.

Formaldehyde.  Yes there is a small amount of formaldehyde is all flu vaccines.  But, small amounts of formaldehyde is present in the human body already.  According to CHOP,
"First, formaldehyde is essential in human metabolism and is required for the synthesis of DNA and amino acids (the building blocks of protein). Therefore, all humans have detectable quantities of natural formaldehyde in their circulation (about 2.5 ug of formaldehyde per ml of blood). Assuming an average weight of a 2-month-old of 5 kg and an average blood volume of 85 ml per kg, the total quantity of formaldehyde found in an infant's circulation would be about 1.1 mg, a value at least five-fold greater than that to which an infant would be exposed in vaccines."
Finally, in my research on the flu shot I came across a great post from healthyfellow with more options for preventing the flu.


Look at the CDC, FDA, and CHOP sites for more information.
Jefferson T, Di Pietrantonj C, Rivetti A, Bawazeer GA, Al-Ansary LA, Ferroni E. Vaccines for preventing influenza in healthy adults. Cochrane Database of Systematic Reviews 2010, Issue 7. Art. No.: CD001269. DOI: 10.1002/14651858.CD001269.pub4.

Manzoli L, Ioannidis J, Flacco M, De Vito C, Villari P. Effectiveness and harms of seasonal and pandemic influenza vaccines in children, adults and elderly: A critical review and re-analysis of 15 meta-analyses. Human Vaccines & Immunotherapeutics 2012; 8:851 - 862; PMID: 22777099; http://dx.doi.org10.4161/hv.19917.

Osterholm MT, Kelley NS, Sommer A, Belongia EA.  Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis.  The Lancet Infectious Diseases - 1 January 2012 ( Vol. 12, Issue 1, Pages 36-44 ) DOI: 10.1016/S1473-3099(11)70295-X  

No comments:

Post a Comment