Recommendations for the Seasonal and H1N1 (Swine Flu) Influenza Virus Vaccines

The influenza virus is the culprit behind the seasonal ailment referred to as "the flu." The virus causes a collection of symptoms such as, general body aches, fever, headache, and chest pain. Although the common cold is also caused by a virus and has some overlapping symptoms, it can be differentiated from the flu by its lack of body aches and high fever. Most individuals can fight the flu virus off with no problem other than the inconvenience of having the symptoms the virus induces; however, in others it can be severely debilitating or even lethal. The virus is virulent, or strong, enough to lead to the death of approximately 36,000 people annually in the U.S., usually in elderly individuals with a weak immune system ill prepared to fight off viral infection. Unlike the common cold virus however, a vaccine is available to prompt our immune system to neutralize the virus.

In addition to the seasonal influenza virus, this flu season (2009-2010) will include the newly emergent H1N1, or "swine flu" virus. The swine flu virus is transmitted in exactly the same manner and causes similar symptoms as the seasonal flu. The moniker, "swine flu", was give to the virus because it contains influenza genes commonly found in the flu virus that afflicts pigs. The fear is that swine flu may be more dangerous than the seasonal flu because the human immune system has never encountered the swine genes expressed by the virus. This is in contrast to the seasonal flu virus for which an infected individuals' immune system may retain some cross-reactivity to the virus from year to year to at least curb the severity of the infection.

The seasonal injection based influenza virus vaccine is produced as a new batch annually, as the virus surface proteins change slightly enough from year to year to evade the immune system's memory. The vaccine is created by propagating the influenza virus in chicken eggs, from where it is purified, followed by inactivation to prevent the collected virus from causing infections. The vaccine is formulated at a specific concentration of inactivated virus in prefilled syringes for ease of administration. The swine flu, or H1N1, vaccine will be formulated in the exact same manner and by the same manufacturers as seasonal flu.

A common question that arises every flu season is: should I get the flu vaccine? The Centers for Disease Control (CDC) has very specific recommendations for who has priority to receive the injectable vaccine for seasonal and swine flu. For seasonal flu, the CDC recommends individuals over the age of 50, children between 6 months to 19 years of age, pregnant women, people living in nursing homes, those with conditions where the flu could lead to death or severe debilitation, health care workers, and people who care for children less than 6 months of age should have first priority to receive the seasonal vaccine.

For the injectable swine flu vaccine, the recommendations are very similar to the seasonal vaccine, although there are subtle differences. The CDC recommends first priority for people between 6 months and 24 years of age, pregnant women, individuals between the ages of 24 and 64 years who have conditions making them susceptible to debilitating or deadly flu infections, health care workers, and people who care for children under the age of 6 months. Having second priority to receive the swine flu vaccine are people 65 or older and healthy individuals between ages of 24 and 64. Current data suggests that younger individuals are more likely to get swine flu than people older than 65, in contrast to the seasonal flu.

The CDC states that people who should not receive the injectable seasonal or swine flu vaccine are those that are allergic to chicken eggs, have had previous severe reactions to the vaccine, are under the age of 6 months, and those that have developed the neuron damaging Guillain-Barré syndrome after a previous influenza immunization.
A newer formulation of the flu vaccine that is composed of live-attenuated virus is available as a nasal spray. Like the injectable vaccine, it will be available for both seasonal and swine flu. This formulation can only be used in healthy individuals between the ages of 2-49 that are not pregnant. The live-attenuated vaccine is thought to be more effective than the injectable inactivated influenza vaccine in children and less so in adults.

If more information on this topic is desired, several links are provided below and contain very detailed information on both the seasonal and swine flu vaccines. Questions about the vaccine or influenza virus should also be directed towards your physician or local pharmacist.

References and Additional information:

Center for Disease Control and Prevention - Seasonal Flu. http://ww.cdc.gov/flu/. accessed 10/7/2009.

Center for Disease Control and Prevention - H1N1 Flu. http://ww.cdc.gov/h1n1flu/. accessed 10/7/2009.

How do they make the influenza vaccine? http://www.influenza.com/Index.cfm?FA=Science_History_6. accessed 10/7/2009.

Inactivated Influenza Vaccine: What you need to Know. http://www.needletips.org/vis/2flu.pdf. accessed 10/7/2009.