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H1N1(Swine Flu): Norway Virus Mutation; Seasonal Flu Vaccine Offers Moderate Protection Against H1N1

November 24, 2009

PUBLIC HEALTH SIGNIFICANCE OF VIRUS MUTATION DETECTED IN NORWAY

On November 20, the WHO briefing #17 discussed the widely talked about mutation in Norway.  The Norwegian Institute of Public Health informed WHO of a mutation detected in three H1N1 viruses.

  • The viruses were isolated from the first two fatal cases of pandemic influenza in the country and one patient with severe illness.
  • Norwegian scientists have analyzed samples from more than 70 patients with clinical illness and no further instances of this mutation have been detected.
  • This finding suggests that the mutation is not widespread in the country.

The good news? The virus with this mutation remains sensitive to the antiviral drugs, oseltamivir and zanamivir, and studies show that currently available pandemic vaccines confer protection.

Worldwide, laboratory monitoring of influenza viruses has detected a similar mutation in viruses from several other countries, with the earliest detection occurring in April. In addition to Norway, the mutation has been observed in Brazil, China, Japan, Mexico, Ukraine, and the US.

Although information on all these cases is incomplete, several viruses showing the same mutation were detected in fatal cases, and the mutation has also been detected in some mild cases. Worldwide, viruses from numerous fatal cases have not shown the mutation. The public health significance of this finding is thus unclear. The mutations appear to occur sporadically and spontaneously. To date, no links between the small number of patients infected with the mutated virus have been found and the mutation does not appear to spread.

Scientists in the WHO network of influenza laboratories are assessing the significance of the mutation. Changes in viruses at the genetic level need to be constantly monitored. However, the significance of these changes is difficult to assess. Many mutations do not alter any important features of the virus or the illness it causes and for this reason, WHO also uses clinical and epidemiological data when making risk assessments.

Although further investigation is under way, no evidence currently suggests that these mutations are leading to an unusual increase in the number of H1N1 infections or a greater number of severe or fatal cases.  Laboratories in the WHO Global Influenza Surveillance Network closely monitor influenza viruses worldwide and will remain vigilant for any further changes in the virus that may have public health significance.

http://www.who.int/csr/disease/swineflu/notes/briefing_20091120/en/index.html

DEPARTMENT OF DEFENSE STUDY: SEASONAL INFLUENZA VACCINATION MODERATELY EFFECTIVE AGAINST INFLUENZA A (H1N1)

I thought this was a very interesting study but it has gotten very little press.  I think part of the issue is that with seasonal flu vaccine being in short supply, it is not really an option for most people.  If you got a seasonal flu shot this year, it looks like you might have gotten a bonus!

A “moderate degree of protection” against influenza A (H1N1) was seen among military personnel who received seasonal influenza vaccination, according to results of a Department of Defense study presented at the American Society of Tropical Medicine and Hygiene’s 58th Annual Meeting in Washington, D.C.

The results showed that the inactivated vaccination and the live attenuated vaccination were associated with similar levels of protection against influenza A (H1N1). Researchers at the Department of Defense conducted a surveillance study of influenza-related medical issues among military personnel stationed in the United States between April 2009 and October 2009.

During the study period, 1,205 cases of influenza A (H1N1) were reported among military personnel stationed in the United States. According to the researchers, overall vaccine effectiveness of seasonal influenza vaccination against influenza A (H1N1) was 45%.

The results were adjusted for gender, age, number of prior vaccinations and vaccine type. According to the researchers, further analysis indicated that irrespective of prior vaccination status, older age (defined as patients aged older than 39 years) and prior vaccination were significantly associated with increased vaccine effectiveness.

The results also showed that vaccine effectiveness against severe disease outcome (defined as requiring hospitalization) was higher than against milder outcome (defined as requiring outpatient treatment).

So, what is the net-net of this study?   if you can find a seasonal flu vaccine, I would get one!

http://infectiousdiseasenews.com/article/50808.aspx

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