Friday, August 28, 2009

H1N1 flu shots

Coming soon to your neighborhood supermarket: An ounce of prevention against H1N1.

More precisely, .0000005 ounce of prevention which is the teensy-weensy amount of killed viral material that scientists from the CDC, National Institutes of Health, and various licensed pharmaceutical companies inserted into syringes as they launched clinical trials of newly manufactured H1V1 vaccine earlier this month. They expect to analyze study results from mid-September to mid-October and then begin the first public immunization programs before Halloween. The trials will provide important information on the vaccine's safety, efficacy, and whether one or two doses are needed to provide optimal protection. (Study results released 9/10/09 indicated that one dose for adults is sufficient.)

We already know that H1N1 influenza, first identified in Mexico in late winter of this year, is the most common cause of flu-related illness throughout the world at this time. While this new viral strain continues to cause low-levels of new cases in all 50 states, it is currently 'widespread' in Maine and Alaska. But the regular flu season has not even started yet, and once the usual seasonal blend of influenzas A and B hits, we can expect a double whammy of flu-driven illness this fall into winter.

Quite a few of you have called our office with logistical questions about how best to protect yourselves and your families against this onslaught of respiratory crud. Here's the latest information:

What can we expect?

We know that H1N1 flu is quite contagious, easily passed person to person via contaminated secretions from coughs and sneezes, and able to survive on surfaces for up to 8 hours. While the initial reports from Mexico were quite disturbing with respect to the severity of illness caused by this strain, the illness lately has been acting a lot like seasonal flu. It does disproportionately affect persons under 60 and and can be unusually virulent in those under 25. Per Dr. Jay Butler of the CDC, "75% of the [H1N1]hospitalizations are in those aged under 49 and 60% of the deaths are in those under age 49." Studies showed that no young adults demonstrated circulating antibodies to H1N1 at the start of this pandemic whereas many older adults apparently encountered a similar influenza variety in the past and were found to have some immunity to this strain.

Experts are unable to estimate the community prevalence of H1N1 as many cases are too mild to come to medical attention. In addition, as H1N1 becomes more prevalent, the CDC no longer recommends that such mild cases be tested to confirm the presence of this specific virus.

As I've mentioned in previously posts, influenza is a tricky and changeable foe which can mutate rapidly. Thus far, thankfully, studies of the virus from recent cases in the southern hemisphere demonstrate no significant genetic change from northern cases investigated earlier this year.

What's the difference between H1N1 and the seasonal flu?

H1N1 is a novel strain originating in swine (but not caused by consumption of pork!) that developed in North American pigs through the mixing in their respiratory tracts of genetic material from swine, human, and avian flus. It is antigenically distinct from seasonal flu which means that its proteins and genetic material are completely different than the ordinary influenza types that circulate each winter season.

Will I need shots for both?

Absolutely. Separate shots will be available for seasonal and H1N1 flu. Preliminary information released in an online version of The New England Journal of Medicine 9/10/09 indicates one dose will be sufficient for adults; the proper dosing for children is not yet available.

The seasonal flu shot and the H1N1 shot can be taken on the same day--but different arms please! The seasonal shot is already available, however, whereas the first H1N1 vaccines will not be distributed until late October. While the optimal time to receive the seasonal flu shot is October or November to assure that immunity lasts through the entire season, the CDC currently recommends that persons receive the seasonal vaccine as soon as possible to assure that both flu shots can be administered to the largest number of people.

How can I get the H1N1 vaccine?

While the CDC was hopeful that ample vaccine would be available by October, production delays will slow delivery of adequate vaccine until later on in the year. For this reason, certain groups have been assigned top priority for the first wave of vaccinations, chosen due to their risk for more serious disease. These include:
  • Pregnant women
  • Persons who live with or provide care for infants aged <6>
  • Health-care and emergency medical services personnel with direct patient contact
  • Children aged 6 months--4 years, and
  • Children and teens aged 5--18 years who have high risk medical conditions

What about college-aged children?

The CDC and universities are implementing various programs to limit the spread of H1N1 disease on campus. Some Colorado schools will offer alternative housing for dorm residents whose roommates become ill.

Stay tuned for up-to-date information on the use of anti-viral medications such as Tamiflu for H1N1 prevention and treatment.


JeanMac said...

Best info I've read on this nasty flu.
It clarified for me the need for 2 shots - we'll be standing in line:)

Anonymous said...


Margaret Kowalski said...

Finally, a blog that isn't trying to sell me something! From my personal experiences as a physician, I've learned that flu shots are very important for all people, especially the elderly and young children. Thanks for posting this great info :)