AVIAN FLU UPDATE

                  

                                  [From Microbe 2008 3:218-219]

    Now that the 2007-2008 seasonal flu seems to be over, what can we say about the status of avian flu (H5N1)? That is, can we say that this flu is drawing to an end also? Unfortunately, the answer is no! According to the World Health Organization (WHO), in 2007, avian flu caused 86 cases along with 59 fatalities. Indonesia and the Nile Valley in Egypt accounted for most of these cases with additional ones being reported from China, Vietnam, among others. WHO officials recorded another 23 human cases in 2008 with 18 of these being fatal. According to Nancy Cox of the Centers for Disease Control and Prevention (CDC), avian flu is off to a rapid start in 2008.

    Avian influenza, although relatively rare and deadly in humans, has been circulating widely in domestic poultry and wild bird populations particularly in Asia and the Middle East. Needless to say, this situation has provided ample opportunity for genetic variants to occur. Currently, these variants consist of 9 distinct groups (or clades) of which viruses from any one of these clades could be triggered as causing a pandemic. It goes without saying that all of these H5N1 variants, along with a variety of other questions and uncertainties, have complicated vaccine readiness plans. For example, flu experts are now talking about both  “pre-pandemic” and pandemic vaccines; first, the pre-pandemic vaccine to help prevent deaths and, next, the pandemic vaccine to inhibit severe infections. The vaccine Prepandrix, developed by Glaxo Smith Kline Biologicals, can initiate protective immune responses against H5N1 influenza and is deemed acceptable for human use. In fact, this is one of several such vaccines targeted to help European member states “prepare for pandemic influenza.”

    Since none of these vaccines is felt to be ideal nor exactly what populations are to receive them, several questions have arisen as to when and how to use them. The antigens in several of these vaccines have proven to be poor in their protective capacity on their own but can be enhanced when adjuvants such as aluminum hydroxide are added. It all comes down to when and how to use one or more of these experimental H5N1 vaccines in humans. Indeed, it is conceivable at least in European and U.S. populations that there is likely a greater risk from being immunized with these vaccine(s) than contracting the avian flu. Also one has to consider whether these products will be able to adequately protect against any number of the highly infectious-in-humans variants of H5N1 if the need to use them ever arise. The FDA has given notice that the new adjuvants being used with these vaccines will be subjected to an intense review process. Whatever safety requirement(s ) are imposed will have to be carefully balanced against the goal of inducing high host-immune responses while allowing for the fact that higher levels of antibodies could very well broaden the response to protect against anyone particular H5N1 variant(s) that could arise and potentially decimate public health as we currently know it.

Author: Nick Knisely

Episcopal bishop, dad, astronomer, erstwhile dancer...