Flu Shots Target Wrong Strain But Still Worth Having Says CDC

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Main Category: Flu / Cold / SARS
Also Included In: Immune System / Vaccines;  MRSA / Drug Resistance
Article Date: 11 Feb 2008 - 12:00 PDT

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As the flu season gets into full swing across the United States, the Centers for Disease Control and Prevention (CDC) said that while this year's shots do not match all of the major circulating types of flu, they are still worth having because as a minimum, they lessen the severity of the illness and protect against serious potential complications.

Dr Joe Bresee, chief of epidemiology and prevention at the Influenza Division of the CDC, told reporters on Friday that the flu vaccine will not directly target two of the three types of flu virus circulating this season, but it is still important to take it because it offers some protection and can make the difference, especially to vulnerable people, between having a severe illness with complications and a mild one.

According to the University of Minnesota's Center for Infectious Disease Research & Policy (CIDRAP), Bresee said that even when the match between vaccine and flu strain is less than ideal, there is still some "cross-protection", and this was particularly true for high risk groups:

"Getting a flu vaccine may reduce the risk of death or hospitalization from the disease," said Bresee, who also, according to WebMD said that:

"While vaccination is the best way to prevent flu, good hand hygiene and flu etiquette are also effective in preventing flu transmission."

According to the CDC's latest weekly influenza season report, during week 5 of the season (from 27 January to 2 February 2008), 31 states reported widespread flu, 17 states reported regional activity, and two states and the District of Columbia reported local influenza activity.

Although the flu season is well under way, it still has not peaked, argued Bresee because if you look at the trends in hospital admissions, outpatient illnesses and deaths, they are still going up. Bresee told WebMD that he would not be surprised if the trends continued upwards for several weeks.

Since September 2007, the CDC has identified 197 different flu viruses in circulation in the US (101 type A (H1N1), 53 type A (H3N2) and 43 type B).

Of the 43 type B viruses, 40 of them were from the Yamagata strain and only three from the Victoria strain, the target of this year's flu vaccine.

The H1N1 strain circulating this year is so far a good match for the vaccine, said the CDC.

Bresee explained that it's not easy to predict which strains are going to be circulating in the next flu season, and yet a choice has to be made nearly a year in advance in order for vaccines to be produced on time. He said the World Health Organization is already working on which strains to recommend as targets for next year's vaccines.

Two new trends however are causing doctors and health authorities to be extra vigilant this flu season. One is the rise in staph, and resistant strains such as MRSA in particular, as side complications in children with flu, and the other is the emergence of vaccine resistant flu strains.

Nearly 5 per cent of circulating influenza strains have become resistant to Tamiflu one of the two major flu drugs. So far Relenza, the other major flu vaccine, has not met any resistance.

One child is confirmed to have died of flu this year, said Bresee, who added they were expecting another five child deaths due to flu will be confirmed in the next few days. The agency does not know if the deaths are MRSA related. Last year, 15 of the 73 child deaths were MRSA related.

"This reminds us all that influenza is a common disease and can be a severe disease," Bresee told reporters.

Click here for more information about seasonal flu (CDC).

Sources: WebMD, CDC weekly seasonal flu report FluView, CIDRAP news report.

Written by: Catharine Paddock, PhD


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