Two new strains to be used in 2006-07 flu vaccine

Mar 1, 2006 (CIDRAP News) – Global and US health authorities have recommended two new influenza virus strains for use in the flu vaccine for the 2006-07 season.

Last week the US Advisory Committee on Immunization Practices (ACIP) selected a "Wisconsin" strain of influenza A(H3N2) and a "Malaysia" strain of influenza B for next season. They will replace a "California" strain of H3N2 and a "Shanghai" strain of influenza B used in the current vaccine.

The "New Caledonia" strain of influenza A(H1N1) virus used in this year's vaccine should be used again next season as the third component of the trivalent vaccine, the ACIP said. (The strain's full name is A/New Caledonia/20/99[H1N1].)

The ACIP, which advises the Centers for Disease Control and Prevention (CDC), followed recommendations from the World Health Organization (WHO) and the Food and Drug Administration (FDA) in picking the strains. The CDC routinely follows the ACIP recommendations on flu vaccines.

Each February the WHO assesses the flu virus strains in circulation before picking the strains for the next Northern Hemisphere flu season. In a Feb 14 report on its recommendation concerning the H3N2 strain to be used, the WHO said, "Many recent isolates were antigenically similar to the current reference virus, A/California/7/2004, but an increasing proportion of recent viruses was more closely related to A/Wisconsin/67/2005."

Likewise, the WHO said the majority of recent influenza B isolates were similar to the strain B/Malaysia/2506/2004, rather than to the B/Shanghai/361/2002 strain used in this year's vaccine. The Malaysia strain is antigenically equivalent to B/Ohio/1/2005, according to the CDC.

A year ago, health authorities picked only one new strain for the 2005-06 flu vaccine, keeping the other two the same. According to a recent Reuters report, a spokesman for a leading vaccine manufacturer said changing two of the strains in next season's vaccine may make production less predictable.

"It does put more uncertainty into the total number of doses you're producing at any one time," Albert Thomas, director of vaccine manufacturing for Sanofi Pasteur, was quoted as saying. His company has been the biggest supplier for the US market in recent years.

The strains to include in each season's vaccine must be chosen early in the year because it takes roughly 6 months to produce the vaccine. The viruses used in vaccines are grown in chicken eggs.

The WHO report said global flu activity from October 2005 through January 2006 was low compared with recent years. Several countries had outbreaks of H3N2 influenza, but H1N1 and B viruses caused only scattered cases in most countries, the agency said.

See also:

Feb 23 CDC news release on ACIP actions, including flu vaccine recommendation
http://www.cdc.gov/media/pressrel/r060223.htm

WHO report on recommendation for 2006-07 vaccine
http://www.who.int/influenza/vaccines/2007northreport.pdf

Feb 17, 2005, CIDRAP News story "FDA approves adding new strain to flu vaccine"

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