The Doctor Is In: H1N1 Vaccine

My husband is a pediatrician.  Once a week(or so) I share this space with him so that he can give you up-to-date and  pertinent information about a variety of medical topics.  If there are topics that you would like to see him address, please email me at queenofhaddock(at)gmail(dot)com.

***Disclaimer – this is my personal statement regarding influenza and includes things that I tell my own patients/parents in visits to my office. This is not meant to be a substitute for a visit to or discussion with your pediatrician. For any questions regarding your child’s health you should of course discuss them with your pediatrician. This is meant only to provide information, which I hope you find helpful.***

So there have been a ton of questions regarding the H1N1 flu vaccine.  There are a lot of concerns over whether or not it is a safe vaccine, if it has been tested enough, etc.  Let me go ahead and say that the H1N1 vaccine is just as safe as the seasonal flu vaccine.  As far as whether or not it has been “tested,”  we already have years of clinical experience with the seasonal influenza vaccine, and the H1N1 vaccine is prepared in exactly the same manner as seasonal flu vaccine.  (For my previous post on influenza, go here).

To understand how the vaccine works, let’s go over a little background information on the virus.  The flu virus has on its surface proteins that help it to cause infection and duplicate itself.  For influenza A, these are hemagglutinin and neuraminidase.  Hemagglutinin plays a role in helping the virus to attach to cells in our body, and neuraminidase plays a role in allowing the virus to penetrate into the cells and start using the machinery of our cells to reproduce itself.  These unique proteins help to type the virus.  The “swine flu” virus that is circulating this year has hemagglutinin 1 (H1) and neuraminidase 1 (N1) on its surface, therefore it is termed “H1N1.” These two proteins on the surface of the virus change slightly every year from either mutations in the DNA that code for them (termed “antigenic drift”) or occasionally change greatly by recombination of genes between two different types of flu viruses (termed “antigenic shift”).  If the flu was exactly the same every year then after your immune system saw it one time with infection or immunization, then re-exposure would allow the immune system to recognize it and attack it before it caused infection.  These yearly subtle changes in the surface proteins are what allow the flu to evade our immune system, appearing as a “new” virus that the immune system does not recognize.  This is why you have to get a flu vaccine every year.  Information is collected every year on what strains of flu virus were the most common circulating strains.  Using the prior years’ trends to predict which strains will most commonly circulate in the coming year, the flu vaccine is prepared with these proteins from what is believed will be the most common flu virus strains for the upcoming flu season.  The flu vaccine has to be incubated for months using eggs, which is why the flu vaccine isn’t always perfect in preventing flu.  Sometimes the best models for predicting which flu virus strains will circulate aren’t 100% accurate, so therefore neither will the vaccine be.  Even if the vaccine isn’t perfect, some protection may still be provided.  One might ask why not wait and see which strains show up at the start of flu season, which would be a reasonable question.  The issue there is that if we waited until we knew which strains would be circulating, then by the time the vaccine was ready after months of incubation, flu season would be over.  For more detailed information on how the viruses for the seasonal flu vaccine are chosen go here.

That brings us to the H1N1 vaccine.  Unlike the seasonal flu, we know which surface proteins are present on the virus (H1N1!!) and therefore the vaccine is specific for the swine flu strain.  The vaccine is prepared in exactly the same manner as the seasonal flu vaccine, and therefore is just as safe to receive.  There are two types of vaccine – the injectable vaccine and the nasal spray (FluMist).  For H1N1 specific information on each vaccine click here for info on the shot and here for info on the nasal spray vaccine.  Much more information in the H1N1 vaccine may be found here

The exact timing of availability of the H1N1 vaccine will vary by state, but in general the higher risk populations will be targeted first

• Pregnant women
• Household and caregiver contacts of children younger than 6 months of age (e.g. parents, siblings, and daycare providers)
• Health care and emergency medical services personnel
• Persons from 6 months through 24 years of age
• Persons aged 25 through 64 years who have medical conditions associated with a higher risk of influenza complications

(Above target groups via http://www.cdc.gov/h1n1flu/vaccination/clinicians_qa.htm)

This grouping does not mean that you won’t be able to get it if you’re not in one of the above groups.  As production of the vaccine continues the supplies will eventually cover all those who desire it.  Early on, however, supplies will be limited.  Therefore the initial target groups are those at higher risk from complications of infection.   Currently in the state of Georgia healthy children aged 2-4 are being targeted to receive the intranasal (FluMist) vaccine, as they are among the most common group responsible for transmission of the virus to others.  Check with your pediatrician or local health department to see if/when the vaccine is available for you or your child.

In deciding whether or not to be vaccinated or to have your children vaccinated, know that it is a safe and effective vaccine.  Also consider that while H1N1 has not been the great pandemic killer it was feared to be, there’s always the possibility, however remote, than the virus may mutate or acquire a gene that allows it to cause much more severe disease (this was what caused the 1918 strain to be so deadly – it had a particular gene that provided it much higher virulence).  Now is the time to be vaccinated before such an event occurs.

One other thing that should not be overlooked is that the H1N1 vaccine only protects against the H1N1 flu virus.  It does not protect against the seasonal flu virus, which is still out there circulating.  If you want to be protected from the seasonal flu virus, you will need to be immunized with the seasonal flu vaccine in addition to the H1N1 vaccine.